</ 



-URANOGRAPHY; 



OR, 



A DESCRIPTION OF THE HEAVENS; 



0£S IGNED FOR 



ACADEMIES AND SCHOOLS; 



ACCOMPANIED BY 

AN ATLAS OF THE HEAVENS, 

SHOWING THE PLACES OF THE PRINCIPAL STAR9, 
CLUSTERS, AND NEBULJE. 

BY 

#^ 

E. OTIS KENDALL, 

PROFESSOR OF MATHEMATICS AND ASTRONOMY IN THE CENTRAL 

HIGH SCHOOL OF PHILADELPHIA, AND MEMBER OF THE 

AMERICAN PHILOSOPHICAL SOCIETY. 



PHILADELPHIA: 

PUBLISHED BY E. H. BUTLER & CO. 

1850 






Entered, according to the Act of Congress, in the year 1844, by 

E. H. BUTLER, 

Hi the clerk's office of the District Court of the United States in 
and for the Eastern District of Pennsylvania. 

By Traitf* 

Mil 3" 



J. Fagan, Stereotyper. 



C. Shercnan, PriDter. 



/^ 



v- 



USA* 



\P 



TO 

ALEXANDER DALLAS BACHE, LL.D., 

SUPERINTENDENT OF THE U. S. COAST SURVEY, AND LATE PRINCIPAL 
OF THE PHILADELPHIA HIGH SCHOOL, 

DISTINGUISHED ALIKE FOR HIS ATTAINMENTS IN SCIENCE, HIS ZEAL IN 

ITS ENCOURAGExMENT, AND HIS SUCCESSFUL LABOURS 

IN THE CAUSE OF POPULAR EDUCATION. 

THIS WORK 

IS, BY PERMISSION, VERY RESPECTFULLY DEDICATED, BY HIS FRIEND 
AND OBEDIENT SERVANT, 

The Author. 



PREFACE. 



In offering to the public this brief description of the 
heavens, it has been my aim to make the work as 
simple and popular as possible. It is, of course, not to 
be expected that it can present much claim to novelty 
or originality. I shall be satisfied if the descriptions 
are true, and easily understood by the younger class 
of learners. The want of such a treatise has been felt 
while endeavouring to furnish popular instruction to 
the pupils of the High-School in this place. The Atlas 
of the Starry Heavens, published in 1839, in German, 
by J. J. Von Littrow, the distinguished Director of the 
Vienna Observatory, was used for some time as a basis 
of a course of oral instruction. The excellence of 
Littrow's Atlas, and of his method of describing the 
heavens, induced me to undertake the translation of 
the entire work. The maps have been re-engraved 
with English names of the constellations, and with 
such modifications as my experience had suggested. 
On comparing, however, Littrow's text with the most 
recent publications, particularly the Micrometric Mea 
sures of the celebrated Struve, I found that the progress 

Ciii) 



IV PREFACE. 

of knowledge in the department of double stars has 
been so rapid of late, that it was necessary to write 
anew all that part which relates to this important por- 
tion of the sidereal heavens. This I have done in con- 
formity with the most recent publications of Struve 
and Msedler. Another important modification of Lit- 
trow's method was required. He refers to another 
more extensive publication under the title of the 
" Wonders of the Heavens." I have extended this de- 
scription of the heavens so as to embrace a portion of 
the interesting subjects treated of in that work. In 
doing so, I have written anew the chapters on the 
general description of the nebulae, and clusters of stars, 
chiefly from English authorities, among whom I men- 
tion with pleasure the papers of the elder and younger 
Herschel ; — the popular treatise of the latter, on astro- 
nomy, and Madam Somerville's work on the "Con- 
nexion of the Physical Sciences." In writing a treatise 
on Uranography, aiming to be simple and popular, I 
have thought it necessary to furnish, in each constella- 
tion, a method of finding the principal stars in the hea- 
vens by the process of lining. In these descriptions no 
novelty could be expected, and no other merit than 
that of simplicity has been aimed at. The position of 
the stars in the figures is adapted to this Atlas. The 
figures do not in all instances occupy the same place 
and size among the stars as in other Atlases and Globes. 
They rest, however, on the authority of the celebrated 
German astronomer Littrow. One important advan- 
tage will be found in this Atlas over most others ; the 



PREFACE. V 

faint outlines only of the figures are given, and the 
boundaries of the constellations. On a first glance at 
the maps, the stars are the prominent objects which 
strike the eye, and the pupil is not distracted in his 
efforts to learn the constellations, by missing in the 
heavens the objects made too conspicuous on the map. 
The number of the maps is so full that there is little 
distortion of the relative positions of the stars. It may 
seem almost preposterous in a work which attempts to 
give an epitome of the sublime discoveries of the Her- 
schels and of Struve, that the fabulous history of the 
almost useless figures in the constellations should be 
interwoven ; they form, however, a part of the history 
of the progress of the human mind in one of its noblest 
studies, and as such must ever claim a place in a popu- 
lar treatise like the present. While aiming to insert 
all that is requisite to aid trie steps of the beginner in 
astronomy, the claims and wants of the amateur have 
not been quite neglected. The text, in finer print, con- 
tains a selection of the most important and interesting 
double and multiple stars, nebulae and clusters, in each 
constellation, so described that any person having a 
telescope may select as types some which are suited to 
its capacity, and those who have no instrument may 
be furnished at once with such a description as the best 
instruments afford. 

The work is simply descriptive of the heavens: to 
have attempted a treatise on practical astronomy, or 
the use of instruments, would have made the work too 
complex and voluminous. Those who wish to culti- 



Yl PREFACE. 

vate the study of practical astronomy may avail them- 
selves of Gummere's Astronomy, (edition of 1842), 
Mason's Supplement to Olmsted's Astronomy, and 
Bowditch's Practical Navigator. Those who are not 
possessed of the British Nautical Almanac, will find a 
valuable auxiliary in Downes' United States Almanac 
or Complete Ephemeris, which contains numerous 
examples of useful computations in practical astro- 
nomy. 

Philadelphia, April 23, 1844. 



TABLE OF CONTENTS. 



PART I. 
Sec. 1. — General Description of the Heavens. 

Page 

Appearance of the Starry Heavens 11 

Horizon, Zenith, Meridian 12 

North Pole, Circumpolar Stars, Pole Star 13 

Diurnal motion of the Heavens, Celestial Sphere 13 

Sec. 2. — Preliminary Definitions. 

Axis of the Heavens, Celestial Equator, Geometric Poles.. 14 

Division of the Circle 14 

Declination Circle, Vertical Line, Zenith and Nadir .... 15 

Meridian of a place, Vertical Circle, Ecliptic 15 

Equinoxes, Equinoctial Colure, Right Ascension 16 

Declination 16 

Sec. 3. — Constellations. 

Origin of Constellations — their antiquity 17 

Geography, Uranography 17 

Littrow's Figures, Bayer's Designation of the Stars .... 18 

Changes in their Magnitudes 19 

Sec. 4. — Magnitudes of the Stars. 

Division of Stars into Magnitudes 19 

Herschel's Classification, Struve's do 20 

(vii) 



Vlll CONTENTS. 

Sec. 5. — A more particular Description of the 
Starry Heavens. 

Brilliancy of the Stars, Twinkling 20 

Planets. Fixed Stars — their number 21 

Description of Uranography 22 

Use of a Celestial Atlas . . . . 22 

Comparative Brilliancy of Stars of different Magnitudes. 23 

Bode's Distribution of Stars 23 

Harding's Atlas. Number of Telescopic Stars 24 

Their tendency to appear in Groups 25 

Sec. 6. — Double and Multiple Stars. 

Tendency of Stars to appear in Pairs 25 

Mitchel's and Herschel's Opinions of Double Stars 26 

Herschel's Discoveries, Argelander's Investigations 26 

Authors of Works on Double Stars 26 

Herschel's Method of Computing their Orbits 27 

Encke's Method, Maedler's Labours 27 

Number of Double Stars — Physical Connexion 27 

Ternary, Binary, Multiple Stars, &c 27 

Stars Optically Double or Multiple 28 

Revolutions of the Double Stars 28 

Prevalence of Newtonian Gravity 28 

Solar and Stellar Systems compared 28 

Number of Double Stars above the 8th Magnitude 29 

Struve's Number of Stellar Systems 29 

Maedler's recent Estimate 30 

Sec. 7. — Comets. 
Reference to Section 22 30 

Sec. 8. — Variable Stars. 

Definition, Catalogue, Mira Ceti 31 

Algol, and other Variable Stars 32 

General Remarks, Causes of their Variations 34 

New and Lost Stars 35 



contents. ix 

Sec. 9. — Nebula and Clusters of Stars. 

Remarkable Groups, Milky- Way 36 

Its Nature and Formation 37 

Supposed Position of the Sun in the Milky- Way 38 

Resolvable Nebulae, Globular Clusters 39 

Irresolvable Nebulae, Annular do 40 

Planetary and Stellar Nebulae, Nebulous Stars 41 

Zodiacal Light supposed to be a Nebulosity 42 

Clusters of Nebulae 42 

Double Nebulae, Number of Nebulae 43 

Their supposed Origin 43 

General Remarks 44 

Sec. 10. — Description or the Maps. 

Maps of the Northern and Southern Hemispheres 45 

Explanations of the Maps 46 

Maps of the Northern Hemisphere, Plates III. to VII. . . 46 

Maps of the Equatorial Regions, Plates VIII. and IX.. . 46 

Maps of the Southern Hemisphere, Plates X, to XIV. . . 46 

Map for Lining, Plate XV 47 

Sec. 11. — Description of the Constellations. 

Plate I.— -Northern Hemisphere. 

Plate II. — Southern Hemisphere. 

Plate III. — Constellations. 

Ursa Minor — The Little Bear 47 

Cepheus— The King 48 

Draco — The Dragon 49 

Lacerta — The Lizard 51 

Honores Frederici — Frederick's Honours 52 

Canes Venatici — The Grey-Hounds 52 

Quadrans Mural is — The Mural Quadrant 52 

Cygnus — The Swan 53 



X CONTENTS. 

Plate IV. — Constellations. 

Ursa Major — The Great Bear 57 

Custos Messium — The Guardian of the harvest 59 

Camelopardalis — The Giraffe 59 

Cassiopeia? — The Lady in her Chair 60 

Leo Minor — The Little Lion 62 

Lynx — The Lynx 62 

Perseus et Caput Medusae — Perseus and Medusa? s Head,* 63 

Tarandus — The Reindeer 65 

Telescopium Hersehelii — HerscheVs Telescope 65 

Plate V. — Constellations. 

Pegasus — The Flying Horse 6Q 

Andromeda — Andromeda 68 

Triangula— The Triangles 69 

Musca— The Fly 70 

Pisces— The Fishes 70 

Aries — The Bam 71 

Plate VI. — Constellations. 

Auriga — The Charioteer 73 

Taurus— The Bull 74 

Cancer— The Crab 76 

Orion — Orion 78 

Gemini— The Twins 81 

Monoceros — The Unicorn 82 

Canis Minor— The Little Dog 83 

Plate VII. — Constellations. 

Bootes — The Herdsman 84 

Lyra— The Harp 86 

Hercules — Hercules 88 

Corona Borealis — The Northern Crown 90 

Taurus Poniatowski — The Polish Bull 91 

Leo Major — The Great Lion 99 



CONTENTS. XI 

Plate VIII. — Constellations. 

Virgo — The Virgin 94 

Coma Berenices — Berenice's Hair 100 

Sextans— The Sextant 102 

Plate IX. — Constellations. 

Antinous — Antinous 103 

Aquila— The Eagle 103 

Libra— The Scales 104 

Serpentarius vel Ophiuchus — The Serpent-bearer 105 

Serpens — The Serpent 108 

Delphinus— The Dolphin 109 

Equiileus — The Little Horse 110 

Scutum Sobieski — SobieskVs Shield 110 

Turdus Solitarius — The Solitary Thrush Ill 

Vulpecula et Anser — The Fox and Goose Ill 

Sagitta— The Arrow 112 

Plate X. — Constellations. 

Sagittarius — The Archer 113 

Scorpio — The Scorpion 114 

Lupus— The Wolf 115 

Ara— The Altar 116 

Norma, vel Quadra Euclidis — The Rule 116 

Telescopium — The Telescope 116 

Corona Australis — The Southern Crown 116 

Plate XL — Constellations. 

Aquarius — The Water-bearer 117 

Capricornus — The Goat 119 

Piscis Australis — The Southern Fish 121 

Globus JErostaticus — The Balloon 121 

Microscopium — The Microscope 121 

Grus— The Crane 121 

Phosnix — The Arabian Bird . .• 121 

Apparatus Sculptoris — The Sculptor's Tools 121 

Indus — The Indian 122 



Xll CONTENTS. 

Plate XII. — Constellations. 

Cetus— The Whale 129 

Eridanus— The River Po . 124 

Lepus— The Hare 125 

Harpa Georgii — George's Harp 125 

Sceptrum Brandenburgium — Sceptre of Brandenburgh.. 126 

Apparatus C hemic us — Chemical .Apparatus 126 

Machina Electrica — Electrical Machine 126 

Caela Sculptoris — The Graver 126 

Horologium — The Clock 127 

Plate XIII. — Constellations. 

Canis Major— The Great Dog 127 

Argo Navis— The Ship Argo. 129 

Columba— The Dove 130 

Felis— The Cat 130 

Equiileus Pictoris — The Painter's Easel 130 

Officina Typographica — The Printing Press, 131 

Pyxis Nautica — The Mariner's Compass 131 

Plate XIV. — Constellations. 

Hydra— The Water- Serpent 131 

Crater— -The Cup 133 

Centaurus — The Centaur 133 

Coitus— The Crow 134 

Antlia Pneumatica — The Air Pump 135 

Robur Caroli — Charles' Oak 135 

Crux— The Cross 135 

Sec. 12. — The Calendar of Stars. 

January 137 

February 140 

March 143 

April 146 

May 1 48 

June 150 



CONTENTS. Xlll 

July 153 

August > 156 

September 159 

October 162 

November 164 

December 166 

Sec. 13. 
Telescopic appearance of Double Stars 169 

Sec. 14. 
Portions of the Heavens rich in Stars 170 

Sec. 15. 

Clusters of Stars 172 

Stellar Nebulae 174 

Double Nebulae 177 

Hollow Nebulae 178 

Irresolvable and Planetary Nebulae 179 

Other remarkable Nebulae 182 



PART II. 

Sec. 1. 
General Description of the Solar System 185 

Sec. 2. 
Ptolemaic System 186 

Sec. 3. 

Copernican System 187 

Ancient Opinion regarding the Figure of the Earth .... 188 

Rotundity of the Earth demonstrated 188 

Proof of the Earth's Diurnal Revolution ; 189 



xiv contents. 

Sec. 4. 

Definitions 190 

Sec. 5. 

Kepler's First Law 195 

Definitions of the Ellipse 195 

Kepler's Second Law 196 

Illustration of Orbital Motion 197 

Kepler's Third Law 197 

Sec. 6. 

Newtonian Theory of Gravitation 198 

Principle of Gravitation 199 

Extension of the Law of Gravity to the Stars 200 

Sec. 7. 

The Sun 201 

Figure of the Sun 202 

Diameter and Revolution on its Axis 202 

Opinions concerning the Nature of the Sun 203 

Zodiacal Light — its Phenomena 203 

Force of Gravity at the Surface of the Sun 204 

Proper Motion of the Sun 205 

Sec. 8. 

Mercury — Rotation upon his Axis — his Distance 206 

His Diameter 207 

Distinction between Inferior and Superior Planets 207 

Greatest Elongation of Mercury 207 

Transits of Mercury 208 

Density of Mercury 209 

Force of Gravity at its Surface 210 

Ancient Names of this Planet 210 

Sec. 9. 

Venus — its Distance, Rotation and Magnitude 211 

Brilliancy of Venus ••••«•••••• 211 






CONTENTS. XV 

Great Vicissitudes of its Seasons 212 

Transits of Venus 213 

Sun's Parallax as deduced from these Transits 214 

Effects of the small Eccentricity of its Orbit 214 

Various Names of Venus 215 

Sec. 10. 

The Earth — its Distance from the Sun, and Diameter. . 215 

Its Mass, Density and Figure 216 

The Motions of the Earth 217 

Day and Night 218 

The Seasons 220 

The Earth's Satellite 222 

The Atmosphere 222 

Cause of Winds 224 

Change of Position of the Earth's Axis in the Heavens 225 

Polar Stars 225 

Second Variation in the Position of the Earth's Orbit. . 227 

Definition of Perturbation 227 

Third Variation of the Position of the Earth's Perihelion 227 
Mythological Names of the Earth 228 

Sec. 11. 

General Remarks concerning Secondary Planets 228 

Points of Resemblance with their Primaries 229 

Equality of their Periods of Revolution and Rotation . . 230 
Appearances of the Primary Planet viewed from its Se- 
condaries 231 

Force of Gravity upon the Secondary Planets 232 

Sec. 12. 

The Moon 232 

Its Revolution, Diameter, and apparent Motion 233 

Libration in Longitude and Latitude 234 

Phases of the Moon 235 

Eclipses — Harvest Moon 237 

2 



XVI CONTENTS. 

Appearances of the Heavens as seen from the Moon. . . 238 

Eclipses at the Earth and at the Moon compared 240 

Description of the Moon's Surface 241 

Lunar Caverns — Crater-formed Elevations 242 

Lunar Volcanoes — Central Mountains 243 

Heights of Lunar Mountains 244 

Sec. 13. 

Mars — its Distance from the Sun — Diameter, &c 245 

Inequality in the length of its Seasons 247 

Its Days also unequal 248 

Transits of inferior Planets seen from Mars 248 

Mythological Names of this Planet 249 

Sec. 14. 

Vesta — its Diameter — Distance from the Sun, &c 250 

Its Mythological History 250 

Sec. 15. 

Juno — its Place in the System, and its Orbit 251 

Number of its Names among the Ancients 251 

Sec. 16. 

Ceres — its Description and Mythology 252 

Sec. 17. 

Pallas — its Place in the System 252 

The great Inclination of its Orbit — its ancient History.. 253 

Sec. 18. 

General Remarks concerning the Asteroids 253 

Their Periods of Revolution 255 

Force of Gravity at their Surfaces very small 256 

Sec. 19. 

Jupiter — its Diameter, Period of Revolution, &c 257 

Effects of the great centrifugal Force at its Equator. . . . 258 



CONTENTS. XVH 

Difference of the Seasons and of the length of Days. . . 258 

Intensity of Light and Heat 259 

Brightness of Jupiter 259 

Telescopic Appearance 259 

Jupiter's Satellites 261 

Their Diameters 261 

Apparent Motions of these Satellites 262 

Their combined Light not equal to that of the Moon. . . 263 

Mythological History of Jupiter 264 

Sec. 20. 

Saturn — its Distance from the Sun, Diameter, &c 265 

Dimensions of its Rings 266 

Telescopic appearance of the Planet 266 

Rotation of the Rings 267 

Cause of their elliptical Appearance 267 

The Rings must be irregular Solids 268 

Appearance of the Rings from the Planet itself ....... 269 

Force of Gravity at the Surface of Saturn 270 

Satellites of this Planet 271 

Their Phases , 271 

Their Eclipses 272 

Their Periods of Revolution 273 

The Mythology of Saturn 274 

Sec. 21. 

Herschel, or Uranus 275 

Its Appearance to the unassisted Eye 275 

Its mean Distance from the Sun — its Diameter, &c. . . . 275 
The apparent Diameter of the Sun as seen from Uranus. 276 
Amount of the Annual Parallax of the Fixed Stars for 

Uranus 277 

Peculiarity of the Uranian System regarding the Satel- 
lites 277 

Phases of the Satellites 277 

Their Eclipses 278 



XV111 CONTENTS. 

Density of Uranus 278 

Distances and Periods of Revolution of the Satellites. . 278 

Mythological Account of Uranus 279 

Sec. 22. 

Comets — Origin of their Name 280 

Number of Comets 280 

Heads of Comets 281 

Their nebulous Envelopes 282 

The Tail of Comets 282 

Apparent Lengths as seen from the Earth 283 

Estimated real Lengths 284 

Origin of the Envelope and Tail 284 

Dissipation of the Substance of Comets 286 

Popular Superstitions respecting Comets 286 

Elements of the Orbits of Comets 288 

Average Inclination of their Orbits 288 

Probability that Comets move in Ellipses 289 

Periodical Comets 290 

Halley's Comet — its supposed Appearances 291 

Its certain Appearances 292 

Olbers' Comet — when discovered, &c 293 

Encke's Comet — its observed Returns 294 

Proof of a resisting Medium obtained by means of this 

Comet 295 

Gambart's Comet 296 

Cause of its invisibility in 1839 296 

Comets supposed to be periodical 297 

Third Comet of 1843 298 

Peculiarities of this Comet 299 

Instability of the Position of its Orbit 300 

Sec. 23. 

Eclipses of the Moon — their Cause 301 

Partial, total and central Eclipses 301 

The Shadow of the Earth 302 






CONTENTS. XIX 

Duration of a Lunar Eclipse 302 

Description of the Plate, Fig. 1 302 

Difficulty of observing with exactness a Lunar Eclipse. 304 

Eclipses of the Sun — how caused 305 

Description of the Plate, Fig-. 2 305 

Central, total and partial Eclipses 305 

Annular Eclipses 306 

Number of Eclipses in a Year 307 

Sec. 24. — Tides. 

High and low Tides— Spring Tides 308 

Neap Tides 309 

Tide Wave 310 

Causes of the Neap Tides 312 

Heights of Tides in various Places 315 

Co-tidal Lines — Unit of Altitude 316 

Establishment of a Port — Atmospheric Tides 317 

Appendix. 

Elements of the Orbits of Binary Stars 319 

List of Stars which, from their Relative Motion, are sup- 
posed to form Stellar Systems 320 

List of Stars supposed from their Proper Motion to form 

Stellar Systems , -. . 323 

Elements of the Orbits of the Planets 324 



DIRECTIONS TO THE BINDER. 



Mars, Jupiter, and Saturn Frontispiece. 

Gamma Virginis to face page 96 

p of the Serpent Bearer 

Phases of Venus 

Seasons 

Phases of the Moon 

Phases of Saturn 

Great Comet of 1811 and 1819 

Great Comet of 1843 



106 
212 
221 
235 
267 
286 
298 



(xx) 



PART I. 

SEC. 1. 

GENERAL DESCRIPTION" OF THE HEAVENS. 

The starry heavens, on a clear evening, present 
to an observer the appearance of the hollow sur- 
face of a vast hemisphere, in the centre of which he 
is placed, and which is bounded by the seemingly 
circular plane on which he stands. This plane 
appears to meet the heavens in a distant circular 
line which is called the horizon. In this hollow 
surface we see the sun by day, the moon some- 
times by day, sometimes by night, and the planets, 
stars and comets, by night only. A slight degree 
of observation will show that all these objects 
partake of a common apparent motion from east 
to west. 

If we turn towards the south, we may observe 
some star rising a little to the east of south ; and 
if we watch its course, we shall find that it ascends 
for a time until it has reached a point towards 
the south at a little distance above the horizon, 
and then descends gradually till it sets in the 
west, — the points of the horizon at which it rises 

(ii) 



12 GENERAL DESCRIPTION 

and sets, being equally distant from the southern 
point. If we observe, in the same manner, a star 
which rises farther from the southern point than 
the preceding, we shall find that it follows a simi- 
lar path, except that it attains to a greater height 
and continues longer visible. The arc or path in 
which it appears to move, is parallel to that of 
the former, but larger. A circle drawn from the 
south point, perpendicular to the horizon, will 
bisect or divide into two equal portions all the 
arcs described by the stars, while above the hori- 
zon it will pass through the point directly over 
head, called the Zenith, and continuing down- 
wards, will cut the horizon in the north point. 
This circle is called the Meridian. It corresponds 
to the geographical meridian prolonged in every 
direction to the stars. If w T e continue our obser- 
vations upon the stars as they rise at different 
points of the eastern portion of the horizon, we 
soon discover that the paths they describe are all 
parallel to each other and bisected by the meri- 
dian, — that the segment or visible portion of the 
circle described by any one star, is greater in 
proportion to its distance from the south point, at 
the moment of rising, — that a star which rises 
near the north point of the horizon, will describe 
nearly an entire circle above the horizon, — and 
finally, that there are many stars above the north- 
ern portion of the horizon which never set, but 
which, if followed with the eye for a number of 
hours, will be found to describe concentric circles 



OF THE HEAVENS. * 3 

that lie wholly above the horizon ; near the cen- 
tre of these circles is a star which appears to 
remain stationary. This is called the Pole Star. 
And all the stars which do not set are called Cir- 
cumpolar Stars. When the pole star is more 
accurately observed with instruments, it is found 
to describe a small circle around a point, at a dis- 
tance of about a degree and a half. This point 
is called the North Pole of the heavens, or simply 
the North Pole. 

If these observations be continued on several 
successive evenings, it will be found that the same 
stars always rise at the same points, and move 
precisely in the same manner from east to west ; 
and that at a given time on any two successive 
evenings, they appear to occupy nearly the same 
positions with reference to the earth, and exactly 
the same positions with reference to each other. 

The appearance of the heavens, therefore, to an 
observer, supposing himself stationary, is that of 
an immense concave sphere, of which he occupies 
the centre, and which revolves, once in about 
twenty-four hours, round an axis, inclined to the 
horizon, one extremity of which axis is the north 
pole. This motion is called the diurnal motion 
of the heavens. The stars appear to be all fixed 
upon the surface of this Celestial Sphere ; while 
the sun, moon, planets and comets, describe dif- 
ferent paths over the surface and among the stars. 
The apparent diurnal motion of the heavenly bo- 
dies is the same as it would be if they were sta- 



14 PRELIMINARY DEFINITIONS. 






tionary, while the earth, situated at the centre of 
the celestial sphere, revolves from west to east 
once in twenty-four hours, about an axis which 
produced would pierce the heavens at the north 
pole. 



SEC. 2. 

PRELIMINARY DEFINITIONS. 

The Axis of the Heavens is the line about which 
the heavens appear to revolve. It passes through 
the centre and axis of the earth. The points in 
which it pierces the heavens are called the North 
and South Poles. 

The Celestial Equator, or simply the Equator, 
is the great circle in which the plane of the earth's 
equator produced would cut the celestial sphere. 
It intersects the horizon at the east and west points. 

The poles of the heavens are the Geometric Poles of the 
equator. Any circle whose centre is the centre of the sphere, 
and whose diameter is a diameter of the sphere, is called a 
Great Circle. The poles of any circle are the extremities of 
that diameter of the sphere which is perpendicular to the 
plane of the circle, or they are points on the surface of the 
sphere equally distant from all points in the circumference 
of the circle. The poles of a great circle are at the distance 
of a quadrant or 90° from all points in the circumference of 
that circle. 

Every circle is considered as divided into 360 
equal parts, called degrees ; each degree into 60 
equal parts, called minutes ; and each minute into 



PRELIMINARY DEFINITIONS. 15 

60 equal parts, called seconds. They are marked 
° ' " — thus: 10° 2! 20" — which is read ten de- 
grees, two minutes, and twenty seconds. 

The Declination Circle of a star is a great cir- 
cle passing through the poles of the heavens and 
the star, and cutting the equator at right angles 
These circles are sometimes called Meridians. 
They are analogous to meridians of places on the 
earth's surface. 

Parallels of Declination are small circles paral- 
lel to the equator. 

A Vertical Line, at any place, is the direction 
assumed by the plumb-line at that place. 

The Zenith and Nadir, at any place, are the 
points above and below the horizon in which the 
vertical line produced would pierce the heavens. 
They are the poles of the horizon. 

The Meridian of a place is the declination cir- 
cle passing through the zenith of the place, cutting 
the horizon at right angles in the North and South 
points. 

A Vertical Circle is a great circle passing 
through the zenith and nadir, perpendicular to the 
horizon. The Prime Vertical is that vertical cir* 
cle which is at right angles to the meridian of the 
place, and cuts the horizon in the east and west 
points. 

The Ecliptic is the path through which the sun 
appears to move annually among the stars from 
west to east. It is a great circle of the celestial 
sphere, the plane of which is inclined to that of 



16 PRELIMINARY DEFINITIONS. 

the equator in an angle of about 23^°. This an- 
gle is called the Obliquity of the Ecliptic. The 
ecliptic cuts the equator in two opposite points, 
called the Equinoxes. The sun passes one of these 
points about the 21st of March, and the other 
about the 23d of September; the former is called 
the Vernal, and the latter the Autumnal Equinox. 
The poles of the ecliptic are two opposite points 
of the celestial sphere, about 23j° distant from 
the poles of the heavens. 

The Equinoctial Colure is the declination circle 
passing through the equinoxes. 

The Right Ascension of a heavenly body is the 
arc of the equator reckoned from the vernal equi- 
nox eastward to the declination circle passing 
through the body. It is precisely analogous to 
the longitude of a place on the earth's surface ; if 
the position of the equinoctial colure at the mo- 
ment be taken on the terrestrial meridian from 
which longitudes are reckoned. Right ascension 
is sometimes estimated in time, allowing fifteen 
degrees for an hour, fifteen circular minutes for a 
minute of time, &cc. 

The declination of a heavenly body is the arc 
of a declination circle intercepted between the 
equator and the centre of the body; or, in other 
words, it is the distance of the body from the 
equator. The declination of an object is called 
North or South, according to its position north or 
south of the equator. Objects on the equator 
have no declination. All objects on the same 



CONSTELLATIONS. 17 

parallel of declination have the same declination. 
The declination of a heavenly body is analogous 
to the latitude of a place on the earth's surface. 

The right ascension and declination of a hea- 
venly body determine its place in the heavens. 
As these terms occur very frequently, they are 
generally, for the sake of brevity, designated by 
R. A. and Dec. 



SEC. 3. 

CONSTELLATIONS. 

For the sake of convenient reference, the hea- 
vens were early divided into constellations, to 
which were assigned, for the most part, names 
celebrated in fable or in history. The origin of 
the constellations is of great antiquity. The old- 
est books that allude to the starry heavens, treat 
of them as being divided into constellations; the 
oldest heathen poets, Hesiod and Homer, mention 
some of them by names that are now familiar; 
and we find Orion and the Pleiades spoken of in 
the book of Job and in the prophecy of Amos. 

In the maps of the stars, the dotted boundary 
line marks the space allotted to each constellation 
in the heavens, in the same manner as nations and 
provinces are designated in common geography. 
Hence works like this are called Geographies of 
the Heavens, according to popular acceptation. 
The word Uranography is more correct; but is 



18 CONSTELLATIONS. 

not much used in popular treatises. The figures 
in the enclosures for the several constellations, 
originally designed for Littrow, are not in every 
instance in the same place as those found on com- 
mon globes, and other atlases of the heavens. To 
avoid confusion in this respect, the descriptions 
of the position of the stars in the figures, are 
adapted to the maps in this book, which rest on 
the authority of this celebrated German astron- 
omer. 

The stars in each constellation are distinguished 
by the letters of the Greek alphabet, -which are 
applied to them in the order of their relative 
brightness ; the principal or brightest star being 
called a, the next /3, &c. In the larger constella- 
tions, after exhausting the Greek alphabet, the 
Roman letters are used, and sometimes numbers. 
Thus : a Lyrae denotes the brightest star in the 
constellation of the Lyre, a Tauri the brightest 
star in the Bull, &c. Many of the principal stars 
are also known by particular names, as : Sirius or 
the Dog Star, a of the Great Dog; Mdebaran or 
the Bull's Eye, a Tauri ; Regulus or the Lion's 
Heart, a Leonis, &c. 

To facilitate the studies of those readers who 
are not familiar with Greek, we here insert the 
alphabet of that language : 

Alpha, .... a ... a Epsilon, . . . s . . . e short. 

Beta, p ... b Zeta, f ... z 

Gamma, ... y ... g Eta, q ... e long. 

Delta, $ ... d Theta, 0,§ . . th 



CONSTELLATIONS. 



19 



Iota, 

Kappa, . 
Lambda, 
Mu, . . . . 
Nu, .... 

Xi, 

Omicron, 
Pi, 



1 

kc 

1 • 

m 
n 
x 

o short. 

P 



Rho, 

Sigma, . . . 

Tau, 

Upsilon, . . 

Phi, 

Chi, ..... 

Psi, 

Omega, . . . 



X 
* 



r 
s 
t 
u 

ph 

ch 
ps 
o long. 



These Greek letters were assigned to the stars by Bayer 
in the beginning of the seventeenth century. They do not 
conform in all instances with the recent classification of the 
stars in the order of brightness by Sir John Herschel. This 
circumstance shows that a ^change has taken place in the 
relative brightness of the stars since Bayer's time. To avoid 
confusion, Bayer's Greek letters are still used. 



SEC. 4. 

MAGNITUDES OF THE STARS. 

The stars are also divided into different orders 
or classes, called Magnitudes, according to their 
relative brilliancy : the brightest stars being said 
to be of the first magnitude ; those a little less 
brilliant, of the second ; and thus the distinction 
is continued to the sixth magnitude, which includes 
the smallest stars generally visible to the naked 
eye. The classification is still extended to the 
telescopic stars, commencing with those of the 
seventh magnitude, which are readily seen in a 
good opera glass, and embracing the smallest stars 
visible in the most powerful telescopes formerly 
used. 



20 



MAGNITUDES OF THE STARS. 



Sir John Herschel uses 14 classes of telescopic stars, his 
smallest being of the 20th magnitude. Struve divides them 
into 6 classes, his smallest being* of the 12th magnitude, the 
same as the 20th of Herschel. Struve follows the analogy 
of the first 6 classes : his 7th class appears in the fourteen 
feet Fraunhofer Telescope, at Dorpat in Russia, as bright as 
a star of the first magnitude to the naked eye. His 12th 
or Herschel's 20th magnitude appears, in such an instru- 
ment, as faint as a star of the 6th magnitude to the naked 
eye. Struve's magnitudes are used in this book. They 
may be adapted to Herschel's scale by means of the follow- 
ing table : 



Struve's Classes. 


Corresponding Classes 
of Herschel. 


1st to 6th 


1st to 6th 


" 7th 


7th and 8th 


" 8th 


9 th and 10th 


" 9th 


11th and 12th 


" 10th 


13th and 14th 


" 11th 


15th, 16th and 17th 


" 12th 


18th, 19th and 20th 



SEC. 5. 



A MORE PARTICULAR DESCRIPTION OF THE STARRY 
HEAVENS. 

If we examine the heavens on a clear evening, 
we find the celestial vault crowded with a vast 
number of stars of various degrees of brilliancy. 
Some are so bright that the eye cannot gaze on 
them steadily. The effect of this dazzling light on 
the nerves of the eye is such as to cause an appa- 
rently tremulous motion of the stars themselves, 



DESCRIPTION OF THE STARRY HEAVENS. 21 

and they are said to twinkle. This serves to dis- 
tinguish these bright stars from another class of 
bodies, of which only one or two are usually visi- 
ble at the same time in the heavens. These, 
though nearly or quite as large as the brightest 
stars, have a softer light, which we are enabled 
to gaze on steadily, and which therefore are said 
not to twinkle. These latter are also found to wan- 
der about among the other stars, and are therefore 
called planets, or wanderers, from a Greek word of 
that signification. The twinkling stars, on the 
contrary, compose groups that always maintain 
nearly the same relative position towards each 
other, and are hence called fixed stars. The fixed 
stars are divided in; 3 six classes, according to 
their degrees of brilliancy. The sixth class con- 
tains the smallest stars which on a clear night 
can be seen with a good eye without the assist- 
ance of a spy-glass or telescope. The number of 
these fixed stars seems at a casual glance to be 
countless, and they are said in common language 
to be " as numerous as the leaves on the trees, or 
the sands on the sea-shore." The attempt of an 
ancient astronomer to count the fixed stars, and 
thus to assign a limit to their number, was sup- 
posed to savour of impiety. A more attentive 
examination of any single group dispels this popu* 
lar illusion, and its numbers are found to be rea- 
dily ascertained. In this way, by counting the 
stars in the several groups that may be seen 
above and around us at once, we find that their 
8 



22 DESCRIPTION OF THE STARRY HEAVENS. 

actual number is less than 2000. Since we see 
less than half of the stars in the concave surface 
of the heavens at once, we might suppose that the 
number of stars in these six classes is not much 
above 4000. In fact, these six classes comprise in 
all only about 3800 stars in the northern, and 
fewer in the southern hemisphere, so that they 
may all be counted in a few hours. The illusion 
produced by a hasty glance is easily explained. 
Each bright star leaves an impression on the eye 
for some moments, and thus by looking around 
the number of impressions is indefinitely increased. 
Not only have all the stars visible to the naked 
eye been counted and classified, but the peculiar 
characteristics of each have been examined with 
the most powerful telescopes, and recorded with 
as much care and attention as those of the princi- 
pal cities of the earth in our geographies. Ura- 
nography, or a description of the various bodies 
in the starry heavens, has now become a part of a 
polite education, as much as geography or a de- 
scription of the places on the earth is of a useful 
one. In both, the aids to a course of study are 
the same. A uranography and celestial atlas or 
map of the heavens are required for obtaining a 
knowledge of the stars. A geography and atlas 
or map of the earth are necessary to obtain a 
knowledge of the globe which we inhabit. 

Besides the six or seven thousand stars of the 
first six magnitudes, a really countless number 
has been revealed to us by the telescope. If we 



DESCRIPTION OF THE STARRY HEAVENS. 23 

take for the seventh class of stars those which in 
the largest telescopes appear as bright as stars of 
the first magnitude to the naked eye, and continue 
with the telescopic stars the analogy with the 
first six classes, we shall have for the 12th class 
the smallest stars visible in any telescope, or those 
which in the largest telescopes appear as bright 
as stars of the sixth magnitude to the naked eye. 

By comparison of the brilliancy of the different 
classes or magnitudes of stars, it is found that if 
sixty-two of the smallest stars visible to the naked 
eye (class sixth) were grouped together so closely 
as to seem like one star, the brightness of the 
group would be equal to that of a star of the first 
magnitude; and 100,000 of those of the 12th mag- 
nitude would be required to produce the same 
degree of brilliancy when similarly grouped. 

If all the stars were of the same size and bril- 
liancy, those of the sixth magnitude should be 
about eight times, and those of the twelfth mag- 
nitude about 300 times as remote from us as the 
stars of the first magnitude. If the stars, besides 
being uniform in size and brilliancy, were also 
distributed at uniform distances in space, we 
might form some conclusion respecting their 
number in each of the twelve classes. Now, 
according to Bode's Uranographia, the stars of 
the first four classes are thus proportionally dis- 
tributed : 

18 of the 1st class, or magnitude. 
52 *« 2d " " 



24 DESCRIPTION OF THE STARRY HEAVENS. 

177 of the 3d class, or magnitude. 

376 " 4th " " 

If we suppose that Harding's Atlas of the Stars contains 
about three-fourths of the whole surface of the heavens, we 
shall have for the next two classes the following numbers. 

1000 of the 5th class, or magnitude. 

4000 " 6th " " 

According to this law of increase, we might expect to find 
among the telescopic stars 

26,000 of the 7th magnitude. 

170,000 " 8th " 

1,100,000 " 9th " 

7,000,000 " 10th " 

46,000,000 " 11th " 

300,000,000 " 12th " 

If actual observation should confirm this estimate, we 
should be led to believe that something like a uniformity or 
average value prevails in the real size and brilliancy of the 
stars, and in their real distance from each other. Now the 
recent examination of the stars in the northern hemisphere by 
Struve with the Pulkovah refractor, shows that there are 
12,800 stars of the 7th magnitude in the northern hemisphere, 
which is about half the above estimate for both hemispheres. 
Again, from the same astronomer's observations at Dorpat, 
it appears that there are not less than 1-20,000 stars of the 
first eight classes between the north pole and the fifteenth 
parallel of south declination. This would leave for the 8th 
class in the whole sphere a number conforming pretty well 
with the above estimate. It seems natural then to suppose 
that such a law prevails. From this examination we may 
conclude that a telescope still more powerful than the Dorpat 
refractor, perhaps the twenty-three feet refractor at Pulkovah, 
which might reveal to us another or thirteenth class of stars, 
would exhibit some two billions more. 

In this manner we may stretch the imagination 



DESCRIPTION OF THE STARRY HEAVENS. 25 

beyond all bounds, and confirm the remark of the 
ancient sage, though on very different grounds, 
that the number of stars in the heavens, as well 
as the distance of the remotest, is really without 
limit. 

Not only do we notice in the heavens this dis- 
tribution of the stars into the classes already enu- 
merated, but we are also struck with their ten- 
dency to present themselves in groups. These 
particular groups or constellations have in all 
ages, and among all nations, received certain 
popular names from a fancied resemblance to 
natural objects. 

This tendency of the stars to the formation of 
groups in the heavens, is too remarkable to be the 
result of accidental distribution in space; but it is 
impossible for us to perceive the immediate cause 
of such a distribution. 



SEC. 6. 

OF THE DOUBLE AND MULTIPLE STARS. 

The same tendency to the formation of groups 
of stars, w^hich is noticed in a casual glance at the 
heavens, is more remarkably displayed on a close 
examination with the aid of the telescope. Pairs 
and multiples. of stars so close to each other as 
only to be seen separately in the most powerful 
telescopes, are found in great numbers. These 



26 THE DOUBLE AND MULTIPLE STARS. 

pairs and groups have been noticed since the first 
invention of the telescope. But it is only recently 
that they have received from astronomers that 
care and attention which their importance de- 
mands. 

In 1767, Mr. John Mitchel expressed a belief that these 
double stars have some peculiar physical connexion with each 
other, and invited astronomers to watch them, and ascertain 
whether the one is not a satellite revolving round the other. 
It does not appear that much notice was taken of this theory. 
In 1780, the elder Herschel commenced the observation of 
these double stars, in order to determine their parallax and 
distance from the sun, by the yearly changes in their distance 
and bearing from each other. He soon found that these 
changes could not be accounted for by the change of place 
of the observer on the earth, in her annual motion round the 
sun. He then attempted to explain them by supposing a 
motion of our sun and system of planets in space. This 
brilliant discovery of the motion of our system in space, by 
Herschel, has since been confirmed by the investigations of 
Argelander, and placed beyond a doubt; but it did not ex- 
plain the motions of the double stars with respect to each 
other. In 1785, Sir William Herschel first suspected the 
true cause of these changes to be a revolution of one of the 
stars round the other, like that of a planet round the sun, con- 
formably to the suggestion of Mitchel. In 1802, he first 
published this discovery to the world with the proofs on 
which it rested. Since that period much labour has been 
bestowed on this subject, by the elder and younger Herschel, 
Struve, South, Bessel, Maedler, and others. The most ex- 
tensive work on double stars was published by Struve, in 
1827, giving a perfect catalogue of 3112 double and multiple 
stars, observed by himself. In 1837, he published another 
work, containing a minute description of each of the pairs 
of stars in his first work. M. Savary first published a me- 



THE DOUBLE AND MULTIPLE STARS. 27 

thod of computing the orbits of the double stars; but to Sir 
John F. W. Herschel belongs the honour of first inventing a 
peculiar method — partly graphic or tentative, and partly ana- 
lytical — of computing these orbits. He applied it success- 
fully to several pairs. Encke has since published an analytic 
method for effecting the same. Encke's method, in the 
hands of Msedler, has been successful in perfecting the first 
sketches of these orbits by the younger Herschel. 

The Appendix will contain Maedler's recent catalogue of 
all the known orbits of these double stars. They will occa- 
sionally be repeated in describing the constellations where 
they occur. 

The number of pairs and multiples of stars 
within 32" of each other, and having one member 
of the system as great as the 8th magnitude, is 
about 4,000, or about one in every forty of the 
stars of the 8th magnitude and upwards. This 
proportion is far greater than would follow from 
a uniform distribution of stars in the celestial 
spaces, as mentioned in the last section, and leads 
us at once to conclude that this great prevalence 
of double and multiple stars must be owing to 
some physical connexion between the individuals 
composing them. Such stars are said to be phy- 
sically double or multiple. They are also called 
binary, ternary, &c. In the nature of things 
there must be another class of double and mul- 
tiple stars, of which one is placed nearly behind 
the other; but perhaps as far beyond it as the 
other is distant from the sun. Such stars — whose 
apparent nearness is the result of their accidental 
position in space, as seen nearly in a line with 



28 THE DOUBLE AND MULTIPLE STARS. 

each other from the earth, and has no relation to 
real proximity or systematic association — are said 
to be optically double or multiple. 

In describing the binary stars, they are said to revolve 
around each other. In reality each revolves around the com- 
mon centre of gravity of the two bodies. When more than 
two stars form a multiple system, they revolve around the 
common centre of the system. It has not been possible as 
yet to determine the comparative masses of the individuals 
composing any of the double or multiple stars : Hence the 
position of the centres of gravity of the multiple systems is 
unknown, and consequently the period of each star round 
that centre is also unknown. But it is customary to say that 
two stars revolve round each other, or the less round the 
greater, whenever the line joining the two stars is found to 
make a complete revolution, returning to its first position after 
every circuit of 360°. 

It has been stated that the pairs or multiples of 
stars in which a change of position or distance 
takes place, are physically double, or multiple. 
They are said to be thus physically connected, 
from their being acted on by some common force 
which causes their motions. This force, in seve- 
ral pairs of double stars, has been shown to be 
that of universal or Newtonian gravity. But 
there is a great difference between these physically 
double or multiple stars and our own solar sys- 
tem ; for we have only one sun with a few planets 
and satellites, while the splendid stellar systems 
are composed of two or more suns revolving about 
a common centre. In some of the stars that are 
physically double, the Newtonian law of gra- 
vity has not yet been shown to prevail ; but 



THE DOUBLE AND MULTIPLE STARS. 29 

from the fact that it extends throughout our solar 
system, and to many of the binary and multiple 
stellar systems, analogy leads us to extend it to all. 
The most remarkable double and multiple stars 
(whether physical or optical) are pointed out in 
the description of each constellation. 

If we suppose an average to prevail in the distribution of 
the stars, with respect to numbers, size, brilliancy, and dis- 
tances apart, there should be in the whole heavens about 
200,000 stars of the first eight magnitudes ; and of these we 
should have, by this law, only one pair of optically double 
stars situated within 4", three pairs from 4" to 8" apart, four- 
teen pairs from 8" to 16", and fifty-four pairs from 16" to 32'' 
apart. Now it is found from actual observation that there 
are, in the region of the heavens north of the fifteenth parallel 
of south declination, the following numbers of pairs of stars 
each of the first eight magnitudes. 
62 stars distant from 

116 " " 

133 " " 

130 " " 

106 " " 

106 " " 

Whereas, by average, there should be only about 48 
optically double stars within this region. The remaining 
605 may be supposed to have some physical connexion 
with each other. The indications of this connexion are a 
change of the bearing or distance of the stars from year 
to year, or something peculiar to the pair in their proper mo- 
tions among the stars. The period through which observa- 
tions have been made is too short to afford a classification 
of all the pairs of double stars in this respect. Struve has, 
however, ascertained that 90 of these stellar systems give 
indications of a periodical change of bearing and distance. 
Doubtless many of the remaining 563 double stars within 



0" 


to 1" 


1" 


to 2" 


2" 


to 4" 


4" 


to 8" 


8" 


to 16" 


16" 


to 32' 



30 COMETS. VARIABLE STARS. 

32" of each other, supposed to be binary, will, in uie course 
of long-continued observations, exhibit proofs of some phy- 
sical connexion. 

Of the triple and multiple stars, nearly all are supposed to 
compose physical systems, since in a distribution of 200,000 
stars at random on the surface of the sphere, only one triple 
or multiple star should be expected to occur within a circle 
of 32" diameter ; whereas 68 triple or multiple stars within 
that limit have been already discovered. The Appendix will 
contain a list of the principal stars known from their relative 
motions to be physically double or multiple, and also a simi- 
lar list of those which are presumed to be such from their 
having the same proper motion among the other stars. Maed- 
ler, in 1843, estimated the number of known binary and 
ternary stars to be about 250. 



SEC. 7. 

COMETS. 

The Comets will be described hereafter. They 
are sometimes seen in the starry heavens; but 
their motions are so extremely irregular as to ex- 
clude them from notice in a general description 
of the heavens. 



SEC. 8. 

VARIABLE STARS. 

There are several stars which, though not 
distinguishable from others by any change of 
place, or by any difference of appearance when 
viewed with a telescope, yet undergo a regular 
periodical increase and diminution of brilliancy. 



VARIABLE STARS. 



31 



These are called variable stars. The following 
table contains the most remarkable stars of this 
kind which have yet been observed, with their 
right ascensions and declinations for 1800, their 
periods, or the number of days elapsing between 
two successive returns to the greatest or least 
brilliancy, and their apparent magnitudes at the 
times of their greatest and least brightness. The 
apparent magnitude indicates that the star is 
invisible at the time of greatest obscurity. 



Star's Name. 


Right Ascen- 
sion. 


Declination. 


Period. 


Magni 


tudes. 


Greatest. 


Least. 


oCeti 


32° 


19' 


3° 


53'S. 


331.96 days. 


2 





j5 Persei . . . 


43 


48 


40 


iin. 


2.8673 


tt 


2 


4 


Leonis . . . 


144 


12 


12 


21N. 


311.4 


a 


5 


10 


Virginis . . 


187 


5 


8 


5N. 


145.46 


a 


6 





Hydree . . . 


199 


42 


22 


15 S. 


494. 


u 


3 





Serpentis . 


218 


4 


15 


3N. 


353. 


it 


8 





Coronae . . 


235 


5 


28 


47N. 


335. 


a 


6 





Serpentis. 


235 


22 


15 


45N. 


340. 


a 


5 





a Herculis. . 


256 


23 


13 


37 N. 


60.5 


a 


3 


4 


Scuti Sob. 


279 


12 


4 


54 S. 


60.6 


a 


5 


7 


/3Lyrae.... 


280 


41 


33 


9N. 


6.44 


u 


3 


5 


yi Antinoi . . 


295 


34 





30N. 


7.17 


(6 


4 


5 


Cygni . . . 


294 


43 


32 


25 N. 


407.5 


(6 


4 





SCephei.. . 


335 


26 


57 


24 N. 


5.36 


a 


3 


4 


Aquarii . . 


353 


32 


16 


23 S. 


382.5 


fit 


6 






The first of these oCeti, or Mira, undergoes the 
greatest change of light, of all the variable stars 
yet discovered, since it varies from the second 
magnitude to invisibility. This remarkable phe- 
nomenon was first noticed by David Fabricius, in 
1596. From a discussion of all the observations 
made upon the light of this star, Professor Wurm 



32 VARIABLE STARS. 

has determined the above period of 331.96 days, 
and given a table for its variations of light. Ac- 
cording to Bianchi of Modena, it attained its great- 
est brilliancy about the 1st of October, 1839. This 
event occurs about a month earlier each succeed- 
ing year. In 1844 it should be most brilliant early 
in May. And its increase of light is much more 
rapid than its decrease. It increases from the sixth 
magnitude to the second in 40 days, and continues 
of this degree of brilliancy 26 days, after which it 
diminishes to the sixth magnitude again in 66 days ; 
hence it is during 132 days greater and during 200 
days smaller than a star of the sixth magnitude. 

The star fB Persei, or Algol, in the Head of Me- 
dusa, is of the second magnitude when at its 
greatest brilliancy, or equal to a Persei above it. 
Its vicissitudes of light are of a kind peculiar to 
itself. It continues visible as a star of the second 
magnitude for the space of 61 hours, then its light 
begins suddenly to diminish, and in 4 hours it be- 
comes of the fourth magnitude, or about equal in 
brilliancy to the neighbouring star p. It remains 
at this magnitude 18 minutes without any sensible 
change, and then in the succeeding 4h. 40m. 
increases to the second magnitude again, in w 7 hich 
state it remains 61 hours. Another peculiarity 
of this star is, that through all its changes it shines 
with a white light, while the colour of all the 
other variable stars is red. 

With the above period of 2.8673 days, and the 
epoch of its least light, 1800, January Od. 17h. 



VARIABLE STARS. 33 

54m. 50.6s., Mean Paris Time, the times of its 
greatest and least brilliancy can be easily com- 
puted for any year. The variation of light expe- 
rienced by this star was discovered by Goodricke, 
in 1783. 

The variable star in the Lion was first observed 
by Koch, in 1780. The increase of its light occu- 
pies 85, and the diminution 140 days. 

The star in the Virgin was first observed to be 
variable by Harding. Wurm determined its pe- 
riod to be 145.46 days, and the epoch of its great- 
est brilliancy 1820, 11th February, at 18 hours 
Mean Paris Time. In this instance also, the 
increase of light is more rapid than the diminu- 
tion. 

The variation in the light of the star in the 
Hydra was first detected by Montanari, in 1672. 

The tw 7 o stars in the Serpent were discovered 
by Harding, in 1828, as variable stars. 

The star in the Crown, discovered by Pigott, 
in 1782, presents a wonderful anomaly in the 
variation of its light. It sometimes remains for 
several years without any apparent change, and 
then again manifestly varies according to the 
period and magnitudes given in the above table. 

The double star a Herculis, or Ras Algethi, was 
found to be variable by the elder Herschel, in 
1795. The increase of its light occupies 22, and 
the diminution 39 days. 

The star in Sobieski's Shield and r t Antinoi, 
were discovered as variable by Pigott, in 1784 



34 VARIABLE STARS. 

and 1795 ; j3 Lyrse and £Cephei, by Goodricke, in 
1784; the star in the Swan, by Kirch, in 1686 
and that in Aquarius, by Harding, in 1811. There 
are, doubtless, many more such stars in the hea- 
vens yet undiscovered. Indeed our knowledge 
of the periods and epochs of many of those in the 
above list is quite imperfect. 

From all the observations hitherto made upon 
changeable stars, it appears that their light is red 
or of a copper colour; that its increase and dimi- 
nution take place with unequal rapidity; that 
their phase of least light lasts much longer than 
that of their greatest light ; and that their periods 
and the brilliancy of the different phases are sub- 
ject to anomalies and perturbations, of the cause 
of w 7 hich we are as yet ignorant. The star Algol 
forms a remarkable exception to these rules, other- 
wise general. 

Various causes have been assigned for this re- 
markable variation of light. Some have supposed 
that these variable stars, like our sun, have a rota- 
tion on their axis, and that one side of them is 
either wholly dark or partly covered with dark 
spots, like those seen on the disc of the sun. 
Others, that these stars are lens-shaped, and that 
their light diminishes or completely vanishes when 
they are turned edgewise towards us. These va- 
riations have also been attributed to atmospheric 
changes, peculiar to these stars. Opaque satel- 
lites intervening might also diminish their light. 



NEW AND LOST STARS. 35 

NEW AND LOST STARS. 

Pliny mentions, in his Natural History, that a 
new star appeared in the heavens about 125 years 
B. C. This circumstance induced Hipparchus to 
make a catalogue of the principal stars, in order 
to enable astronomers to detect similar occur- 
rences in future. In A. D. 389, in the time of Cae- 
sar Honorius, there appeared in the constellation 
of the Eag 1 ^, according to Suspinianus, a star as 
bright as Venus, which remained about three 
weeks and then vanished. In the ninth century, 
two Arabian astronomers saw a new star in the 
Scorpion, as bright as the moon at her quarters. 
It disappeared after about four months. In the 
reign of the Emperor Otho, 945 A. D., the chro- 
nicles mention such a new star, between Cepheus 
and Cassiopeia. A similar star was discovered 
in the same place, i*i 1572, by Tycho Brahe. It 
continued without motion or change of brightness 
for near two years, and then suddenly began to 
wane, and finally disappeared. When first disco- 
vered, it was white, two months afterwards yel- 
low, and finally it became as red as Mars or Alde- 
baran. Before disappearance, its light became 
pale, like that of Saturn. Some have supposed 
the stars of 945, 1264, and 1572, to be the same 
variable star. 

In 1604, a star appeared in the Serpent Bearer, 
nearly as bright as that of 1572. Kepler wrote a 
work on the subject of this star. It disappeared 



36 NEBULAE AND CLUSTERS OF STARS. 

in 1605. In 1670, Anthelm discovered a star of 
the third magnitude in the Swan. At the end of 
two months, it decreased to the fifth magnitude, 
and shortly afterwards vanished. Dominic Cas- 
sini observed this star with great care. 

Many stars mentioned in the old catalogues 
cannot now be found. Some have doubtless dis- 
appeared, and some were probably inserted erro- 
neously in these catalogues. The cause of the 
disappearance of these stars, is matter of mere 
conjecture. Newton supposed that they were 
planets suddenly ignited by coming in contact 
with their suns. 



SEC. 9. 

NEBULA AND CLUSTERS OF STARS. 

The tendency to the formation of groups or 
clusters of stars in the heavens, has already been 
noticed : as examples we may mention the Pleiades 
or seven stars, Berenice's Hair, the Manger in 
the Crab, and the Sword of Perseus. These are 
the most striking groups as seen by the naked eye. 
The Milky-Way abounds throughout in white 
nebulous matter, from which it takes its name. 
This portion, which is white and cloudy to the 
naked eye, is in reality composed of a multitude 
of small stars, whose single light is too feeble to 
make a sensible impression, but when combined 



NEBULJE AND CLUSTERS OF STARS. 37 

in great numbers, they produce the appearance 
of a thin white cloud. 

This illusion is removed by a small telescope, 
which brings to view the individuals composing 
this immense group, and proves that it consists of 
myriads of stars. We may form some idea of 
their number, when we are told by Sir William 
Herschel that 50,000 of them passed through the 
field of his great telescope in the course of an 
hour, in a zone only 2° broad. It was a brilliant 
idea of Herschel, that our sun and its system is 
situated within an immense nebula or cluster of 
stars, perhaps somewhat hollow, of an oval or 
lenticular shape. Succeeding astronomers have 
found that the stars are most widely scattered in 
the portions of the heavens most distant from the 
Milky-Way, and that the condensation or thick- 
ening of the stars increases in approaching this 
region. 

The regular shape of this wonderful zone of 
countless stars, shows that there is an isolated sys- 
tem of suns in the heavens, of which our own sun 
forms a component part. It is probably of the 
form of a lens, having our sun not far from the 
plane passing through the centre. In this plane, 
however, our system is placed at some distance 
from the central part, in a direction towards the 
portion of the milky-way near the constellations 
of Sirius and Orion. No one who glances at this 
portion of the heavens in the winter evenings, 
even without the aid of instruments, can for a 
4 



38 NEBULiE AND CLUSTERS OF STARS. 

moment doubt of the truth of this remark. Per- 
haps the milky-way belongs to the class of hollow 
nebulae, like the annular nebula in Lyra. If our 
system were not situated in the plane passing 
nearly through the centre of the milky-way, we 
should no longer see it as a great zone, but only 
as a smaller portion of the heavens. 

If the sun was placed in the direction of its 
shortest axis, and at a distance as great as its 
longest axis, or diameter of its disc, we should see 
it as a great white cloud of 60° breadth, or of the 
size of the Great Bear. At ten diameters' dis- 
tance it would cover only 6°, and at two hundred 
such diameters' distance it would be no larger 
than some of the nebulae of the first class in the 
heavens, for instance, the nebula in Andromeda 
or Orion. 

The nebulous region of the heavens embraces 
a zone as broad as the milky-way, and perpendi- 
cular to it, passing through the equinoxes. The 
most nebulous portion of this zone is its intersec- 
tion with the constellations of the Virgin and Be- 
renice's Locks. See Plate XVII. Fig. 19th. Here 
the nebulae follow each other in rapid succession, 
by the diurnal motion of the heavens, while in 
some parts of the heavens hours elapse after one 
of them has passed through the field of the tele- 
scope before another enters. 

In examining the heavens with ordinary tele- 
scopes, many small milky-ways or nebulous por- 
tions are seen which, with more powerful instru- 



NEBULA AND CLUSTERS OF STARS. 39 

ments, are resolved into multitudes of stars closely 
clustered together, seeming like a globular space, 
insulated in the heavens and constituting a sys- 
tem by itself, subject only to its own internal laws. 
Many of these resolvable nebnlce have ten thousand 
stars in a surface one-tenth as large as that which 
is covered by the moon, so that its centre where 
the stars are seen projected on each other is one 
blaze of light. 

If all these stars are suns, separated by inter- 
vals as great as that of our sun from the nearest 
fixed star, the distance, which renders the whole 
cluster barely visible to the naked eye, must be 
so great that light would occupy at least a thou- 
sand years in coming to us from this splendid 
assemblage. Occasionally, clusters are so irregu- 
lar in their outline, as merely to suggest the idea 
of a rich portion of the heavens. These contain 
fewer stars than the globular clusters, and fre- 
quently include one much more conspicuous and 
clearly defined than the rest. Sir William Her- 
schel regarded them as the rudiments of globular 
clusters, in a less advanced state of condensation, 
but tending to that form by their mutual attrac- 
tion. 

Multitudes of nebulous spots are seen scattered 
throughout the heavens, having every appearance 
of clusters like those described above, but too 
distant to be resolved into stars by the best tele- 
scopes that have yet been made. Notwithstand- 
ing this circumstance, from their general resem- 



40 NEBULA AND CLUSTERS OF STARS. 

blance to the globular clusters, when seen through 
telescopes of moderate power, they are referred to 
the class of resolvable nebulae. 

Numbers of these nebulous spots give no indi- 
cation of a stellar nature, but appear to be matter 
in the highest possible degree of rarefaction. 
These are denominated irresolvable nebulce. They 
are in every state of condensation, from a vague 
film scarcely to be discerned with the most pow- 
erful telescopes, to such as seem to have actually 
arrived at a solid nucleus. The nebulae of this 
class are of every variety of form and appearance. 
The most remarkable are those represented in 
figs. 59 & 51 , plate XVIII., surrounding the star & in 
the constellation of Orion, and r\ in the southern 
constellation Robur Caroli. The nebulous cha- 
racter of these objects, especially of the former, 
is very different from what might be supposed to 
arise from the diffused light of an immense collec- 
tion of small stars. They resemble light flocky 
masses, like wisps of cloud ; and such wisps seem 
to adhere to many small stars at their outskirts : 
one of them, of a curious form, is represented in 
the figure. These and all the other figures of 
nebulse, are copied from original drawings by Sir 
John Herschel. Some are of an annular form, 
but they are very rare. The most conspicuous 
of these objects is to be found midway between 
f3 and y Lyrae, and may be seen with telescopes 
of moderate power. It is elliptical in the ratio 
of 4 to 5, and is sharply defined. The internal 



NEBULAE AND CLUSTERS OF STARS. 41 

opening, occupying about half its diameter, is not 
entirely dark, but filled with a faint, hazy light. 
Sir John Herschel compares it to fine gauze 
stretched over a hoop. 

Planetary nebulce form another class of very 
extraordinary objects. They have the appear- 
ance of planets; round or slightly oval discs, in 
some instances quite sharply terminated, in others 
hazy and ill defined, and with a light exactly 
equable or a little mottled, occasionally rivaling 
that of the planets in vividness. These nebulse 
are of enormous dimensions. The apparent diam- 
eters of some of them are from 12" to 20"; and 
supposing them to be at the distance of the fixed 
stars, their real magnitudes must, at the lowest 
estimation, be such as to fill the orbit of Uranus, 
which is between three and four billions of miles 
in diameter. 

Stellar nebulce form a fourth class. These have 
a round or oval shape, increasing in density to- 
wards the centre. In some the condensation is 
slight and very gradual ; in others so sudden, as to 
give to the whole the appearance of a star with a 
burr around it, or a candle shining through horn. 
In others the central matter is so highly and sud- 
denly condensed, and so vivid, as to offer the ap- 
pearance of sharp and brilliant stars, surrounded 
by thin atmospheres. These are called nebulous 
stars. There is a very fine example of this class 
in the constellation Andromeda, in R. A. 25° 45', 
Dec. 39° 53' : s and * Orionis are also nebulous* 



42 NEBULA AND CLUSTERS OF STARS. 

but the nebulae can only be seen with very pow- 
erful telescopes. 

The zodiacal light is a thin, lens-shaped atmo- 
sphere, surrounding the sun and extending beyond 
the orbits of Mercury and Venus, which may be 
seen soon after sunset in the months of April and 
May, or at the opposite seasons before sunrise, as 
a cone of light extending obliquely upwards nearly 
in the direction of the ecliptic. This phenomenon 
seems to indicate some slight degree of nebulosity 
about our sun, and even to place it on the list of 
nebulous stars. The stellar nebulae and nebulous 
stars assume all degrees of ellipticity. Some are 
only slightly elliptical ; others much extended in 
length ; and some are long and narrow, like a 
spindle-shaped ray, tapering away at both ends, 
with a bright nucleus in the centre. One of the 
most remarkable specimens of this kind is in R. 
A. 187° 0', Dec. 26° 56'. 

In plates XVII. and XVIII. will be found repre- 
sentations of the most interesting nebulas of all 
classes. A full description of each is given in 
sec. 15. 

The distribution of the nebulae over the hea- 
vens is even more irregular than that of the stars. 
They are most abundant in a zone whose general 
direction is not far from the hour-circle of Oh. and 
12h. Where that zone crosses the constellations 
Virgo, Coma Berenices, and the Great Bear, they 
are assembled in great numbers ; but they are for 



NEBULJE AND CLUSTERS OF STARS. 43 

the most part beyond the reach of any but the most 
powerful telescopes. 

In some instances double or multiple nebulas 
are found presenting a close analogy with the 
binary and multiple stars. It is highly probable 
that such systems of nebulae are bound together 
by some law of attraction, like that which con- 
nects the physically double stars. As yet no 
such law has been detected ; the study is still in 
its infancy, and the double nebulae do not admit 
of precise measures like the double stars. 

The number of nebulae at present known, is 
about 3000. These have all been described by 
the younger Herschel. Of these, near 2000 were 
discovered and described by Sir William Her- 
schel. From comparison of the early and recent 
drawings of the great nebula in Orion, there is 
reason to suppose that a change is going on in its 
appearance, and perhaps in its physical condition. 
Mrs. Somerville remarks, that " the nature and 
use of this nebulous matter, scattered over the 
heavens in such a variety of forms, is involved in 
the greatest obscurity. That it is a self-luminous, 
phosphorescent, material substance, in a highly 
dilated or gaseous state, but gradually subsiding 
by the mutual gravitation of its particles into 
stars and sidereal systems, is the hypothesis most 
generally received. And indeed this is the hypo- 
thesis of La Place with regard to the origin of the 
solar system, which he conceived to be formed by 
the successive condensations of a nebula, whose 



44 NEBULAE AND CLUSTERS OF STARS. 

primeval rotation is still maintained in the rota- 
tion and revolution of the sun and all the bodies 
of the solar system in the same direction. Even 
at this day there is presumptive evidence in the 
structure and internal heat of the earth, of its 
having been at one period in a gaseous state from 
intensely high temperature. But the only way 
that any real knowledge on this mysterious sub- 
ject can be obtained, is by the determination of 
the form, place, and present state of each indi- 
vidual nebula; and a comparison of these with 
future observations will show generations to come 
the changes that may now be going on in these 
supposed rudiments of future systems." 

Having now completed the outline of the vari- 
ous classes of bodies which stud the brilliant vault 
enclosing our own humble solar system, the reader 
will find in the explanation of the maps and the 
descriptions of the several constellations presented 
in the succeeding sections, an available guide in 
the study of the starry heavens. Let him look 
out upon the deep, clear, blue, mysterious Night, 
and with this guide converse with Nature in her 
unfathomable depths. Here he may wander 
among blazing suns, wheeling in awful majesty, 
self-poised, around a common centre in the void 
of space. There, among multitudes of nascent 
orbs of vapour, silent and seemingly motionless, 
but gradually preparing, as it well may be, for 
future usefulness and beauty. Again, where the 
huge planetary nebula spreads out its giant masses 



DESCRIPTION OF THE MAPS. 45 

over an extent of space deemed almost infinite by 
the uneducated, yet reduced by distance to a 
glimmering speck. Let him become familiar with 
these almost unimaginable wonders. Then, re- 
turning in thought to this little ball — invisible 
from the nearest star — on which so many millions 
perpetually contend for power and greatness, let 
him ask for whom, for what, or why was made 
this universe of brightness ! If he be not rendered 
wiser, better, humbler by the enquiry, for him 
these glories have been made in vain. 



sie. i©. 

DESCRIPTION OP THE MAPS. 

The first two maps represent the Northern and 
Southern Hemispheres. In these the graduated 
circle represents the equator ; the centres, the 
poles ; the meridians or declination circles would 
be diameters of this circle ; and the parallels of 
declination, circles concentric with it. The equa- 
tor is divided into degrees, which are numbered 
from the vernal equinox eastward round the cir- 
cle. The meridian passing through 360° and 180° 
is the equinoctial colure ; the lower half of this 
diameter is divided into nine equal parts, these 
divisions corresponding to the even tens of the 
degrees of declination ; they are numbered accord- 
ingly from the equator toward the poles. The 
right ascensions and declinations of the stars may 



46 DESCRIPTION OF THE MAPS. 

be very readily found upon these maps by means 
of a scale and dividers. The R. A. is indicated 
by the point where the radius drawn through the 
star cuts the equator. The Dec. may be deter- 
mined by measuring the distance on this radius 
from the star to the equator, considering the 
radius equal to 90°. 

The next five maps represent sections of the 
northern hemisphere upon the same plan as the 
first, but on a much larger scale. In these the 
parallels and declination circles for every tenth 
degree are drawn. The parallels are numbered 
on two of the meridians, and the meridians around 
the borders of the maps. As the right ascension 
is often expressed in time, each hour being equal 
to fifteen degrees, the corresponding hour is indi- 
cated by the Roman numeral placed without the 
border at each fifteenth degree. 

The eighth and ninth maps represent portions 
of the equatorial regions upon a different plan 
from the preceding, the equator and parallels 
being straight lines, and the meridians also straight 
lines crossing them at right angles. The meridi- 
ans are numbered at the top and bottom, and the 
parallels at the sides. 

The next five represent portions of the southern 
hemisphere ; they are similar to those of the north- 
ern sections. 

The fifteenth contains the principal stars of the 
northern hemisphere, connected by lines so as to 
form a variety of geometrical figures. It is to be 



THE CONSTELLATIONS. 47 

used in studying the positions of the stars by the 
process of lining. 



SEC. 11. 

DESCRIPTION OF THE CONSTELLATIONS. 

PLATE III. 
CONSTELLATIONS. 

Ursa Minor . . . The Little Bear. 

Cepheus .... The King. 

Draco The Dragon. 

Honores Frederici . Frederick's Honours. 

Lacerta .... The Lizard. 

Canes Venatici . . The Grey-Hounds. 

Quadrans Muralis . The Mural Quadrant. 

Cygnus The Swan. 



Ursa Minor— The Little Bear. 
This is a small constellation near the Great Bear. 
In both these the seven principal stars constitute 
a figure called by some a wagon, and by others a 
dipper. In the Little Bear there are five stars of 
the 4th and two of the 5th magnitude, forming 
the little wagon, having the pole star at the end 
of the pole or beam. The four principal stars in 
this constellation are : 

a, Polaris, Ruccaba, or Cynosura. 

(3, Kochab. 

y, Pherkad. 

8, Vildiur. 



48 THE CONSTELLATIONS. 

The Pole Star is of the 2d magnitude, of a yel- 
low colour, and has at the distance of 18" a small 
white star of the 9th magnitude as a companion. 
See plate XVI., Fig. 9. Among the other double 
stars are, 
7t l R. A. 234° 50', Dec. 81° 1', the components are of the 

6th and 7th magnitudes, 30" apart, both yellowish white. 
ft 2 R. A. 237° 26', Dec. 80° 29', 7th and 8th magnitudes, both 

very white, T y apart. 

MYTHOLOGICAL HISTORY OF THIS CONSTELLATION, 

OR 

FABLE. 

The nymph Calisto and her son Areas being 
turned into bears by Juno, Jupiter, to prevent 
their being hurt by huntsmen, transferred them 
to the heavens, in the form of the constella- 
tions Ursse Major and Minor. — Or, according to 
other legends, Cynosura was a nymph of Ida, in 
Crete, who nursed Jupiter, and was by him re- 
warded with a place in the heavens. Thales is 
reputed to have formed the constellation of Ursa 
Minor, by which the Phoenicians are said to have 
sailed ; and for this reason the polar star is some- 
times called Phcenice. 



Cepheus — The King. 

Cepheus is between the Lesser Bear and the 

milky-way. It may be readily known by the 

three stars a, f3, and 7, of the third magnitude, 

which stand nearly in a right line, and by four of 



THE CONSTELLATIONS. 49 

the fourth magnitude, 5, s, £, and Sr, which make 
?. covering for his head. 

a Alder amin. 

/3 Alphirk. 

y Errai. 

|3 is a double star. Its components are of the 3d and 8th magni- 
tudes, distant lS'^the greater greenish white, the smaller blue. 

x is a double star of the 4th and 8th magnitudes, distant 7", 
the greater greenish white, the smaller blue. 

| on the neck, is a double star of the 5th and 7th magnitudes, 
distant 5", the greater yellowish white, the smaller ash- 
green. 

o is a double star of the 5th and 8th magnitudes, distant 2J 
seconds, the greater deep yellow, the smaller deep blue. 
The star 8, in the crown of Cepheus, is variable. In the 

space of two days it changes from the 3d to the 4th magnitude. 
In R. A. 357° 0', and Dec. 60° 16', north of j3 Cassio- 

peiae, is a very rich cluster of stars of 4' diameter. The stars 

of this cluster are nearly all of the 9th magnitude. 

In R. A. 1° 0', and Dec. 71° 35' is a star of the 8th 

magnitude, contained in a well-defined nebular sphere, 20" 

in diameter. 

FABLE. 

Cepheus was an Ethiopian or Indian King, hus- 
band of Cassiopeia, and father to Andromeda, 
He was one of the Argonauts, and changed into 
a constellation after death. He is represented in 
the habit of an Eastern monarch, with a sceptre 
in one hand, and holding his robes with the other. 



Draco — The Dragon. 
This constellation winds itself, with the fore- 
part, around the Pole of the Ecliptic, and with 



50 THE CONSTELLATIONS. 

the other around the Sittle Bear. The Pole of 
the Ecliptic is in R. A. 270°, and Dec. 66° 33'. 
This constellation is composed, for the most part, 
of stars of the 2d, 3d and 4th magnitudes, whose 
situation makes it easily distinguishable. The 
head consists of four stars, two of the 2d and two 
of the 3d magnitude, forming an irregular quad- 
rangle. Between the head and the tail there are 
three coils ; the first, containing nine small stars, 
is about 15° distant from the head, and at about 
the same distance from the Pole as the head ; the 
second and third coils are on opposite sides of a 
line joining the Dragon's head with the Pole Star, 
and about midway between them. These con- 
tain each a star of the 3d magnitude, and several 
smaller ones. Between the third coil and the end 
of the tail are six stars of the 3d magnitude, 
which nearly encompass the Little Bear : they are 
named r„ 0, i, a, x and y, the last being nearly in a 
line joining the Pointers in the Great Bear, a is 
remarkable as having been the Pole Star about 
4600 years ago. 

a Phuban* <r Gianzar. 

(3 Alwaid. p Arrakis. 

y Etamin. I Grumium. 

5 Nodus II jtx Errakis. 
% Nodus I 4^ Dsiban. 

6 Aldib. c Alsaphi. 

Among the double stars are, 
s Its components are of the 4th and 7th magnitudes, dis- 
tant 3", the greater yellow, the smaller blue. 



THE CONSTELLATIONS. 51 

17 vi the 2d and 8th magnitudes, distant 3", recently disco- 
vered by Struve at the Pulkova Observatory. 

p, in the tongue, both white, of the 5th magnitude, distant 4". 

4* of the 4th and 5th magnitude, distant 31 /7 , both white. 
Their proper motion among the other stars is 27" in a cen- 
tury. 
R. A. 248° 3', Dec. 53° 15', in the end of the tongue, near 

*, of the 5th and 6th magnitudes, distant 4" both white. 

FABLE. 

Draco, the offspring of Typhon, with a hun- 
dred heads and as many voices, was the guardian 
of the golden apples which grew in the garden 
of the Hesperides. It was one of the labours of 
Hercules to obtain some of these apples, and he 
slew the Dragon in order to get at them, upon 
which Juno translated the reptile to the heavens. 
This fable is evidently founded upon the part 
acted by the serpent in the fall of our first pa- 
rents ; in consequence of w r hich they and their 
posterity were excluded from the fruit of the tree 
of life, till One greater than Hercules should de- 
stroy him, and restore man to the primeval state 
of innocence and happiness. 



Lacerta — The Lizard. 

This constellation was formed by Hevelius. 

Among the multiple stars are, 

R. A. 337° 3', Dec. 38° 44', a quadruple star; the compo- 
nents are of the 6th, 7th, 10th and 8th magnitudes; the 
two largest are remarkably white, distant 22", the 2d and 3d 
are distant 28", and the 2d and 4th are distant 66". 



52 THE CONSTELLATIONS. 

R. A. 342° 5', Dec. 40° 41', a triple star of the 6th, 12th 
and 9th magnitudes ; the greatest very white ; the two largest 
are 63" apart, the largest and smallest 28". 



Honores Frederici — The Honours of Frederick, 

Formed by Bode, in 1787, in memory of Frede- 
rick II. 



st 



Canes Venatici — The Grey Hounds, 

Is a recent constellation formed by Hevelius. 
It contains none but small stars. 

To the two Hounds which Bootes leads with a 
cord, Hevelius gave the names of Asterion and 
Chara, the former standing towards the north, the 
latter towards the south. To the star a, of the 
3d magnitude, in the Collar of Chara, Halley has 
given the appellation of Cor Caroli, (Charles's 
Heart). 

12 Canum Venaticorum is a double star, whose components 
are of the 3d and 6th magnitudes, both white, 20" 
apart. 



Quadrans Muralis — The Mural Quadrant, 

Is a recent constellation formed by Lalande, in 
memory of the many valuable observations made 
by his nephew at the military school at Paris, 
with a mural quadrant. 



THE CONSTELLATIONS. 53 

Cygnus — The Swan. 
Five of its largest stars, a, /3, y, 8 and s, form a 
cross, by which this constellation is readily known. 
The whole constellation lies in the milky-way, 
besides which the northern part of the Swan is 
very rich in dense clusters of stars. 

a Deneb. 

(3 Mbireo. 

y Sadr. 

s Ginah. 

it Azelfafage. 

In R. A. 314° 52', Dec. 37° 56', between u and 
r, over the right wing of the Swan, stands a re- 
markable double star which is known by the name 
of " 61 Cygni," according to Flamsteed's Catalogue. 
These stars are of the 5th and 6th magnitudes, 
both golden yellow, distant 16". They revolve 
round each other in 540 years. The major axis 
of their elliptic orbit is 30". 8. Both stars have 
moreover a common and very great proper mo- 
tion among the other stars in their vicinity, which 
amounts in a century to 511" in right ascension, 
and 323" in declination, or about 517" in arc. 
This pair of stars will be for ever memorable for 
being the first whose distance from the earth was 
measured with precision. This great discovery 
was made by Bessel from his observations at Kce- 
nigsberg in the years 1837, and 1838, and 1839 
He found their distance 592 000 times the earth's 
mean distance from the sun, and that their light 
5 



54 THE CONSTELLATIONS. 

travels to our system in 9J years. He also con- 
cludes that their two masses are, together, rather 
less than that of our sun. That is to say, that the 
mass of each of them is about one-third. Hence 
our sun seen from 61 Cygni, should appear as a star 
of about the 5th magnitude. Bessel was induced 
to select this pair of stars as the subject of his 
researches, from their great proper motion w r hich 
he justly supposed to be an indication of their 
comparative nearness to our system. In making 
his researches, he compared them with two other 
small neighbouring stars of the 10th magnitude, 
which neither have sensible proper motion, nor par- 
allax ; that is to say, whose distance from our sys- 
tem is immeasurably great. Before this discovery 
was made, Sirius or the dog-star w r as supposed to 
be the nearest because he is the brightest of 
the stars. This may still be the case; but it 
seems more natural to conclude from BessePs dis- 
covery, that the brightest stars are not always 
the nearest, and that they owe perhaps their great 
size and brilliancy to their real greatness of di- 
mensions and intensity of light. In such a case, 
the stars of the first magnitude may possibly be 
many hundred times as great as our sun. 

The attempt to discover the parallax and dis- 
tance of the fixed stars, has been the cause of 
some of the greatest discoveries in astronomy. 
Bradley's discovery of aberration and nutation 
was the result of his researches after the parallax 
of the fixed stars. No other pursuit in astronomy 



THE CONSTELLATIONS. 55 

has engaged so much attention for the last two 
centuries. Bessel is exceedingly fortunate in hav- 
ing brought this long investigation to a successful 
issue. 

The Swan contains many very remarkable double stars. 

fi is a double star, whose components are of the 4th and 
6th magnitudes ; distant 34" ; the greater yellow, the 
smaller blue. 

6 is a double star of the 3d and 8th magnitudes; distant 2"; 
the greater greenish, the smaller ash-coloured. They for- 
merly appeared as a single star ; they are now seen double 
through choice instruments. 

h is a double star, both of the 6th magnitude ; distant four- 
fifths of a second ; recently discovered by Struve, with the 
great Pulkovah refractor. 

fjL is a double star of the 4th and 5th magnitudes ; distant 
6"; the greater white, the smaller bluish white. Both 
stars have the same proper motion of 34" in a century 
among the other stars. 

# in the neck, is a double star of the 5th and 8th magnitudes ; 
distant 26" ; the greater deep yellow, the smaller bluish. 
In 1686, Kirch discovered that the greater is a variable 
star. In 407 days, from being of the 4th magnitude, it 
disappears entirely, and then increases to the 4th magni- 
tude. These two remarkable stars have a proper motion 
of 43" in a century among the other stars. 
In R. A, 287° 30', Dec. 29° 53', is a beautiful, very dense 

group of stars, without any precise nucleus. The whole has 

the form of a triangle, of which the greatest diameter is 3 r . 

This group lies between the head of the Swan and Lyra. 
In R. A. 321° 10', Dec. 50° 50', in the end of the tail, is 

a very large, beautiful, circular group of very small, densely 

clustered stars, in the middle of which there is a reddish star 

of the 8ih magnitude. The whole is about 8' in diameter. 



56 THE CONSTELLATIONS. 

In R. A. 324° 30', Dec. 52° 55', northward from the end 
of the tail, is a very remarkable oval ring of small, densely 
clustered stars. In the middle of the ring stands a reddish 
star of the 8th magnitude. 

In R. A. 302° 15', Dec. 30° 2', midway between the stars 
b and n, is a very large planetary nebula of 15' diameter. It 
is perfectly round, uniformly illuminated, except toward the 
centre, where it is somewhat darker, so that perhaps also this 
object is a planetary ring. 

FABLE. 

Jupiter, in order to deceive Leda, assumed the 
figure of a swan, which he afterwards translated 
to the heavens. Or, according to another fancy 
of the mythologists, Orpheus, after he was mur- 
dered by the wild Bacchantes, was metamorphosed 
into a swan, and placed among the constellations. 



PLATE IV. 
CONSTE LLATIONS. 

Ursa Major . . The Great Bear. 

Custos Messium . The Guardian of the Harvest 

Camelopardalis . The Giraffe. 

Cassiopeia . . . The Lady in her Chair. 

Leo Minor . . . Tlie Little Lion. 

Lynx .... The Lynx. 

Perseus et Caput ) Perseus and Medusa's Head. 
Medusae ) 

Tarandus . . . The Reindeer. 

tt l r- i • • HerscheVs Telescope. 
Herschehi ) r 



THE CONSTELLATIONS. 57 

Ursa Major — The Great Bear. 

The most important stars of this constellation, 
with their proper names, are : 

a Dubhe. x Kaphza. 

f3 Alerak. X Tania Borealis. 

y Phekda. p Tania Australia. 

S Megrez. # Muscida. 

s Alioth. I Alula Australis. 

£ Mizar. v Alula Borealis. 

r\ Benetnash or Alhaid g Alcor. 

i Talita. 

The first seven of these stars, owing to their 
magnitude and remarkable situation, have been 
known from great antiquity under the appellation 
of the Great Dipper; it is also sometimes called 
Charles's Wain. Two of these, a and (3, are de- 
nominated the pointers, because a line drawn 
through them would, if produced, pass very near 
the Pole Star. These seven stars cannot fail to 
be recognized at a glance ; the other principal 
stars may be found by attending to the following 
directions. A line drawn from S through y, and 
produced to the extent of nearly twice their dis- 
tance from each other, will terminate near the star 
4> 5 of the 3d magnitude, in the right hinder leg. A 
line drawn from (3 through ^, and prolonged about 
their distance, will terminate near two stars, § 
and v, of the 4th magnitude, in the left hinder foot. 
The stars p. and X, of the 3d magnitude, in the 
right hinder foot, may be found by conceiving a 



58 THE CONSTELLATIONS. 

right-angled triangle to be formed by joining 4* 
and the two hinder feet, the line joining the two 
feet being the hypothenuse. This hypothenuse 
continued a distance equal to its length from the 
right hinder foot will terminate in the right fore- 
foot where are tw r o stars, i and x, the one of the 
3d and the other of the 4th magnitude. In a line 
joining » with /3, and a little more than one-third 
their distance from i, is the star 6 of the 3d mag- 
nitude, in the right fore leg. The Bear's head, 
which contains two stars of the 4th and five of 
the 5th magnitude, is between the fore-foot and 
the Pole, and on a line w 7 ith 6 and a in the back. 

There are several remarkable double stars in this constella- 
tion. 

f or Mizar, whose components are of the 2d and 4th magni- 
tudes; both greenish white; distant 14". They may be 
seen double in a common spy-glass. Northerly from this 
stands the small star £ called Alcor. 
| or Alula Justralis, in the lower end of the left hinder foot, 
of the 4th and 5th magnitudes ; distant 2". The period 
of their revolution round each other is 60J years. Their 
mean distance is 2 J seconds ; their eccentricity § of this 
distance. Their period is about 20 years shorter than that 
of Uranus. They are also remarkable for their proper mo- 
tion of 74" in a century. 
v of the 4th and 10th magnitudes; very yellow; 7" apart. 

Of the many nebulae of this constellation, the most remark- 
able are the following: 

In R. A. 127° 45', Dec. 50° 49', at the end of the fore-feet, 
is a large, bright, elliptical nebula, of 30' length and 20" 
width, with a light star in the middle. 
In R. A. 145° 15', Dec. 69° 52', on the right ear of the 



THE CONSTELLATIONS. 59 

Bear, a large, light, elliptical nebula, from whose centre rays 
of from 3' to 4' length shoot out. 

In R. A. 175° 45', Dec. 45° 4', southward from the star #, 
a very beautiful, sharply defined, spherical nebula, with a 
bright nucleus. The diameter of the whole is 3'. 

In R. A. 131° 45', Dec. 54° 25', near the star s in the fore- 
foot, a star of the 11th magnitude, with a fan-like nebula 
joined to it. 

In R. A. 200° 30', Dec. 48° 5', under the star q in the end 
of the tail, a very remarkable object and one very difficult to 
determine. A spherical-formed light body, surrounded by a 
concentric nebulous ring, which appears to be broken. 

fable, (See Ursa Minor). 



Custos Messium — The Guardian of the Harvests. 

This new constellation, sometimes called the 
Shepherd, was instituted by Lalande about the 
middle of the last century, in honour of the zeal- 
ous astronomer Messier of Paris. It lies between 
the constellations of Cassiopoeia and the Reindeer, 
and contains only small stars. 

This constellation contains a remarkable quintuple star, 
R.A. 58° 1', Dec. 61° 52'. The two brightest components 
are of the 6th magnitude, distant 18" ; the first white, the 
second bluish white. The three others are of the 9th mag- 
nitude. Their distances are as follows : — 2d and 3d stars, 
49"; 3d and 4th stars, 5" ; of the 4th and 5th, 23". 



Camelopardalis — The Giraffe. 
Was instituted by Hevelius in the beginning 
of the 17 th century, and, like the preceding, con- 
tains only small stars. 



60 THE CONSTELLATIONS. 

Among them we remark a beautiful double star, in R. A. 
64° 40', Dec. 53° 30', between the hoofs of the two hinder 
feet. The two stars are of the 5th and 6th magnitudes, and 
their distance is 10"; the greater appears white, and the 
smaller bluish white. 



Cassiopeia — The Lady in her Chair. 
This constellation is on the side of the Pole Star 
opposite to the Great Bear, and nearly at the 
same distance from it. The five principal stars 

are : 

a Schedir. 
f3 Chaph. 

7 

6 Rueba. 

s 

a, j3 and y form a triangle, right-angled at a; 5 
and s are in a line parallel to the line joining a 
and y, and at the same distance apart as those 
stars. The star /3 is somewhat the brightest of 
the five ; it serves to determine the position of the 
North Pole ; for this star and the Pole star are 
placed on the same side of the true Pole, lying in 
a line with it, while the former is about a degree 
and a half more distant from it than the latter. 
The North Pole is the middle of a line joining /3 
of Cassiopoeia and 6 of the Great Bear. Besides 
these there are several smaller stars, which may 
be easily recognized in the heavens, by observing 
their bearings and distances with reference to the 
five principal stars. 

Northward from the star x Tycho Brahe disco- 



THE CONSTELLATIONS. 61 

vered, about the end of the year 1572, a new, 
very bright fixed star, which, surpassing even Ju- 
piter and Sinus in brilliancy, was visible in the 
daytime, but it gradually became fainter, and 
finally disappeared entirely in March 1574. 

The star p in the left arm, has, among all single 
fixed stars, the greatest proper motion, which 
amounts during a century to 571" in Right Ascen- 
sion, and 150" in Declination. This star has, 
therefore, since the birth of Christ, advanced 
among the other stars about 2° 51', or nearly six 
times the moon's diameter. 

Among the double stars we remark, 
97 the components of which are of the 4th and 8th mag- 
nitudes ; distant 9" ; the greater yellow, the smaller purple. 

These two stars have the same proper motion among the 

other stars, of 119" in a century. 
1 Triple, of the 4th, 7th and 8th magnitudes ; distant 2", 

and 8"; the first is yellow, the others blue. 
4/ Triple, of the 4th, 9th and 9th magnitudes ; distant 32' 

and 3" ; the brightest is deep yellow. 
g in the right arm, of the 5th and 7th magnitudes ; distant 

3" ; the greater deep green, the smaller deep blue. 

R. A. 359° 17', Dec. 57° 28'; of the 8th and 9th magni- 
tudes ; both yellow. They revolve round each other in 95 
years, at a mean distance of 1J seconds. This stellar system 
is called 3042 Struve. 

R. A. 357° 0', Dec. 56° 46', in the head of Cassiopceia, 
stands a beautiful, large, round group of stars, 15' in diame- 
ter. It is a very rich, dense cluster of stars, which are all 
of the 9th and 10th magnitudes. 

R. A. 17° 0', Dec. 57° 26', south of the star S, is found a 
double star of the 8th and 9th magnitudes, at the distance 
of 12'. It stands in the middle of a large spherical nebula. 



62 THE CONSTELLATIONS. 

FABLE. 

Cassiopceia was the wife of Cepheus, and mo- 
ther to Andromeda. She brought upon herself 
the vengeance of the Nereides, by boasting of her 
superior beauty ; and Neptune, at the request of 
those jealous nymphs, sent a huge sea-monster to 
desolate the country. The wrath of Neptune was 
only to be appeased by the exposure of Cassio- 
pceia's beloved daughter Andromeda to the fury 
of the monster; but, just as she was about to be 
devoured, Perseus arrived and delivered her. 
Cassiopceia was, after death, metamorphosed into 
a constellation. She is represented as seated in 
an antique chair, drawing her robe over her shoul- 
der with her right hand, and raising a palm branch 
to her head with her left. 



Leo Minor. — The Little Lion. 

This recent constellation was formed by Heve- 
lius. It consists mostly of smaller stars, of which 
four of the 4th magnitude form a rectangle, by 
which the constellation may be easily known. It 
lies between the Great Bear and the Great Lion. 



Lynx. 



This constellation was also established by He 
velius, and, like the preceding, is composed of 
small stars only. 



THE CONSTELLATIONS. 63 

R. A. 97°, and Dec. 59° 37' is a triple star ; two of the 
stars comprising it are only 2" apart, and nearly 9" each from 
the third. Its components are of the 5th, 6th and 7th mag- 
nitudes. The last two are greenish white, the most distant 
one is blue. 



Perseus et Caput Medusae — Perseus and Medu- 
sa's Head. 

This constellation lies between Camelopardalis 
and Taurus, in the middle of the milky-way. 

a Mirzak, or Algenib, on the breast. 
/3 Algol, in the Head of Medusa. 
| Menchib, in the left calf. 
u JVembus, at the point of the sword. 
o Atix, by the heel of the left foot. 

a, or Algenib, is the brightest star in this con- 
stellation ; it may be easily recognized as being in 
the middle of a tolerably regular curve, formed 
of several stars, concave towards the Great Bear. 
From a towards s of Cassiopceia, and distant from 
it about 5°, is y on the right of the head of Per- 
seus. A line drawn from the Pole Star to 7 and 
produced just one-third their distance, will termi- 
nate in Algol, y, /3 and 5 form a triangle right- 
angled at (5 and nearly isosceles. 

Algol is remarkable for the peculiar changeable- 
ness of its light. At the time of its brightest 
light it is of the 2d magnitude, and nearly equal 
to a above it; 61 hours after it has attained the 
2d magnitude, it suddenly begins to become fainter, 



64 THE CONSTELLATIONS. 

and diminishes in 4 hours to the 4th magnitude. 
It remains in this condition of minimum bright- 
ness 18 minutes, and in the following 4 hours and 
40 minutes, it increases again to the 2d magni- 
tude, in which state it continues 61 hours, and 
then begins to diminish again. 

Among the double stars are, 
s in the left knee of Perseus ; its components are of the 3d 

and 8th magnitudes ; distance 9" ; the greater star is green, 

and the smaller bluish white. The image which this pair 

of stars presents is beautiful and well defined. 
§ of the 3d and 9th magnitudes ; 12" apart; greenish white 

and ash-coloured. 
vi on the right side of the helmet; 4th and 8th magnitudes; 

distance 30"; the greater yellow, the smaller dark blue. 

Both colours very distinct. 
6 4th and 10th magnitudes; 15" apart; the greater star is 

yellow. Proper motion among the other stars 37" in a 

century. 

By 2, in the sword-hand of Perseus, a faint glimmer of 
light may be seen with the naked eye, which, when viewed 
through a telescope, appears as an extraordinarily rich col- 
lection of small and densely clustered stars. The whole 
group forms an ellipse, and has in its centre a double star. 

On the left eye of Perseus we find another beautiful group 
of about 20 stars of the 8th, 9th and 10th magnitudes, with 
many other smaller stars. This group has also a double stai 
at its centre. 

FABLE. 

Perseus, the son of Jupiter by Danae, under- 
took the perilous adventure of destroying the Gor- 
gons, who were represented as three sisters. Of 
these, Medusa alone w T as mortal ; and, though ori- 
ginally a person of great beauty, she had become 






THE CONSTELLATIONS. 65 

so disfigured by a metamorphosis of Minerva, that 
her beautiful locks were changed into snakes, and 
her face was so tremendous that all who beheld it 
were changed into rocks or stones. Perseus, 
however, favoured by the gods, succeeded in his 
undertaking, cut off Medusa's head, and after- 
wards rescued Andromeda from the sea-monster, 
by showing the latter the Gorgon's head, by 
which he was turned into stone. Perseus is repre- 
sented with a sword in his right hand, Medusa's 
head in his left, and a sword at his ancles. 



Tarandus — The Reindeer. 

The Reindeer was established by Lemonnier, in 
memory of the meridian measure completed in 
Lapland, in 1736. This constellation is situated 
between the middle of the Shepherd and the Pole- 
Star, and contains only small stars. 



Telescopium Herschelii — HerscheVs Telescope. 

This recent constellation lies between the Lynx 
and the Wagoner. It was proposed by P. Hell, 
in honour of Herschel and his discoveries in the 
heavens. 



66 



THE CONSTELLATIONS. 

PLATE V. 
CONSTELLATIONS. 

Pegasus .... The Flying Horse. 

Andromeda . . . Andromeda. 

Triangula . . . The Triangles. 

Musca The Fly. 

Pisces The Fishes. 

Aries The Ram. 






Pegasus — The Flying Horse. 

This constellation may be known by four stars, 
one of the 1st and the others of the 2d magnitude. 
They form a regular quadrangle, called the Tra- 
pezium, or sometimes the Table. The North- 
eastern of these four stars is in the head of An- 
dromeda. They are : 

a, Markab. 

(3, S cheat. 

y, Algenib. 

a, Sirrah, (in the head of Andromeda). 
Besides these we remark the following large 
stars : 

s Enif. Bah am. 

I Homan. <r Kerb. 

r) Matar. 
s of the 3d magnitude, in the nose, is at a dis- 
tance from a a little greater than the distance of 
a from y, and nearly in a line with those two stars. 
y\ is also a star of the 3d magnitude, about 5° from 



THE CONSTELLATIONS. 67 

(3 in the prolongation of the line through y and /3. 
£ is equally distant from s and r\, the lines joining 
it with these two stars being nearly at right angles 
to each other. 

% is a double star. Its components are of the 4th and 11th 

magnitudes, 11" apart, both yellow. 

R. A. 320° 30', Dec. 11° 26', a large nebula, very bright in 
the middle, from which streaks of light proceed. 

R. A. 327° 15', Dec. 33° 30', stands another light elliptical 
nebula, 30" long and 9" wide. 

FABLE. 

Pegasus was a winged horse, which, as the 
mythologists pretend, sprang from the blood of 
Medusa when Perseus had cut off her head. He 
became the favourite of Apollo and the Muses ; 
and being afterwards tamed, either by Neptune or 
Minerva, he was given to Bellerophon, when he 
undertook to conquer the Chimera. Having 
achieved this adventure, Bellerophon attempted 
to mount the heavens on his horse, but Jupiter 
sent a gad-fly to sting the animal, so that he dis- 
mounted his rider, who fell headlong to the earth. 
Pegasus, however, continued his flight upwards, 
and was placed by Jupiter among the constella- 
tions. The Jewish Rabbis have a legend of 
Nimrod, very similar to this of Bellerophon, which 
authorizes us to place this constellation among 
the oldest in the sphere. 



68 THE CONSTELLATIONS. 

Andromeda, called also by the Arabs Phoca, 
the Seal. 

This constellation lies between Pegasus, the 
Fishes, and Perseus. The three largest stars in 
it are : 

a Sirrah. 

/3 Mirach. 

y Alamak. 

They stand nearly in a right line, which, pro- 
longed above 7, would pass near Mirzak (a Persei). 
The other principal stars are 6, s and * $ midway 
between a and /3; & and £, in the arms, forming 
nearly a square with a and j8; and f* and v, in a 
line with (3 perpendicular to the line joining y and 
6. All these are of the 4th magnitude except 8, 
which is of the 3d. 

The principal double stars are, 

y or Alamak, which is seen double in common telescopes. 

Its components are of the 3d and 5th magnitudes ; 10" 

apart ; orange-coloured and emerald green. The colours 

are very distinct; a beautiful object. See Plate XVI. 

36 R. A. 11° 24', Dec. 22° 41'; yellow; of the 6th and 7th 

magnitudes ; f" apart. 
59 R. A. 30° 3', Dec. 38° 13'; both bright yellow; of the 
7th magnitude; distant 16". 
R. A. 16° 45', Dec. 48° 5', is a quadruple star of the 7th, 
8th, 8th, and lltn magnitudes respectively, distant J", 10", 
and 30". 

R. A. 8° 15', Dec. 40° 20', Northeasterly over p in the foot, 
is a remarkable nebula. 

R. A. 9° 0', Dec. 42° 57', is a very wide-spread faint ne- 
bula, which embraces about eight square degrees. 



THE CONSTELLATIONS. 69 

R. A. 349° 30', Dec. 41° 30', is a round planetary nebula 
of 12" diameter, with a whitish blue light, and in it is a fine 
double star. 

FABLE. 

Andromeda, the daughter of Cepheus and Cas- 
siopceia, was exposed to be devoured by a sea- 
monster, to appease the wrath of Neptune, but 
was rescued by Perseus, who made her his wife. 
After her death, Minerva changed her into a con- 
stellation. Andromeda is represented by the figure 
of a woman chained by the wrists to a rock. 
Some suppose the fable to be founded on the ad- 
venture of Jonah, who embarked at Joppa for 
Tarshish, to flee from the presence of the Lord, 
but, in consequence of a mighty tempest raised 
by his disobedience, was thrown into the sea and 
swallowed up by a great fish, from which he was 
afterwards miraculously delivered. 



Triangula — The Triangles, 

Lies between the head of Aries and the southern 
foot of Andromeda. It contains only smaller stars. 
The greatest among them is a or Mettallah. This 
is a recent constellation. 

The principal double star is, 
i whose components are of the 5th and 6th magnitudes ; 4" 
apart; the greater is yellow, the smaller blue. This beau- 
tiful pair of stars is situated midway between a and 8. 
They may be seen in good telescopes with illuminated 
field. 



6 



70 THE CONSTELLATIONS. 

Musca— The Fly. 

Between Aries and Perseus ; — a small constel- 
lation, containing one star of the 3d and two of 
the 4th magnitudes. 



Pisces — The Fishes. 

The two fishes are connected by a band ; th* 
one lies between Pegasus and Aquarius, and the 
other between Aries and the head of Andromeda. 
This constellation consists of stars of the 4th and 
inferior magnitudes. 

Among the double stars are, 
a Its components are of the 3d and 8th magnitudes ; distant 

5" ; the greater greenish white, the smaller blue. 
g of the 4th and 5th magnitudes; distant 23"; both white. 

Their proper motion is 11" in a century. 
$ of the 5th magnitude ; both white ; distant 30" ; easily 

seen in common telescopes. 

R. A. 3° 0', Dec. 14° 26', a faint nebula, but extended over 
seven square degrees ; and in R. A. 25° 0', Dec. 5° 4' is a star 
of the 8th magnitude, at the end of a fine, long, straight 
nebulous streak. 

FABLE. 

These Fishes are said by the fabulists to be the 
same that Venus and her son Cupid transformed 
themselves into, to avoid the fury of the giant 
Typhosus, when he assailed the gods on the banks 
of the Euphrates. The character (x) is supposed 
to have the appearance of two fishes tied back to 



THE CONSTELLATIONS. 71 

back ; and the figure is that of two fishes tied by 
their tails, with a loose cord of some length. 

The sun enters this sign about the 19th of 
February. 



Aries — The Ram. 
We recognise this constellation by the three 
large stars in the head of the Ram, about 20 de- 
grees due south of Alamak. 
The principal stars are : 
a Hameh 
(3 Sheratan. 
y Mesarthius. 
Among the double stars are, 
y both of whose components are of the 4th magnitude ; 

very white; distant 9". See Plate XVI. 
s in the hinder part of the back ; both white ; of the 6th 

magnitude ; distant half a second. 
7t in the middle of the thigh, is a triple star, of the 5th, 8th 
and 10th magnitudes; yellowish white; distant 3" and 
25". 
52 Arietis, R. A. 43° 48', Dec. 24° 32', is a triple star; the 
two largest are very white, of the 6th magnitude ; distant 
£ of a second. The third is also very white, of the 11th 
magnitude ; distant b" from the other two. 

FABLE. 

The fabulists pretend that Aries was the ram 
which bore Phryxus and Helle to Colchis, for the 
recovery of whose golden fleece Jason undertook 
the celebrated Argonautic expedition. The ani- 
mal itself, say they, Jupiter snatched up to hea- 



72 THE CONSTELLATIONS. 

ven and formed into this constellation. The cha- 
racter (°f) by which it is marked, is supposed to 
represent the ram's horns. Among the ancient 
Egyptians, Ammon, the symbol of the sun in 
Aries, was represented with a disc over his head. 
The sun enters this sign about the 20th of 
March, which constitutes the vernal equinox, the 
commencement of spring, and the beginning of 
the astronomical year. From this point the right 
ascension and longitude of the heavenly bodies 
are reckoned. It is the opening of the day at the 
North Pole, and the end of day at the South. The 
days and nights are also at this period equal all 
over the earth except at those points. The sun at 
this time has no declination, and is vertical to the 
equatorial parts of the earth. 



PLATE VI. 
CONSTELLATIONS. 

Auriga The Charioteer. 

Taurus The Bull. 

Cancer The Crab. 

Orion Orion. 

Gemini The Twins. 

Monoceros . . . ■ . The Unicorn. 

Canis Minor . . . The Little Dog. 



THE CONSTELLATIONS. 73 

Auriga — The Charioteer, 
With his two Goats. In this we observe a or 
the Goat (Capella or Mhajot), a beautiful star of 
the first magnitude, and f3 or Meukalinam, on the 
right shoulder. With these two stars, 8, in the 
exterior right foot of the Charioteer, or at the ex- 
tremity of the northern horn of the Bull, forms a 
triangle, by which the constellation may be easily 
recognised. Also, the three stars s, £ and v\, form 
a small triangle. 

Among 1 the remarkable objects in this constellation are : 
w a double star. Its components are of the 4th and 8th mag- 
nitudes ; distant 6" ; the greater pomegranate colour, the 
smaller bluish white. 

In R. A. 76° 2', Dec. 32° 29', is a triple star of the 5th, 7th 
and 11th magnitudes; distances 13" and 15"; the greatest 
green, the two smaller bluish white. 

R. A. 74° 15', Dec. 37° 10', stands a well-defined group 
of about 30 stars, with a double star in the centre. 

R. A. 77° 0', Dec. 39° 9', is a rich group of stars, with an 
orange-coloured star in the centre. 

R. A. 80° 0', Dec. 34° 7', is situated a nebula in the form 
of an isosceles triangle, the equal sides being 4" in length, 
with a triple star at the centre of the triangle. 

FABLE. 

Auriga. — Various accounts are given of the 
origin of this constellation. Some suppose Auriga 
to be the same as Phaeton, the son of Sol, who, 
undertaking to drive the chariot of the Sun, set 
the world on fire, and was struck by Jupiter into 
the Eridanus. Others identify him with Erich- 
thonius, the Egyptian king of Athens, the reputed 



74 THE CONSTELLATIONS. 

inventor of chariots and the art of using them 
with horses. He is also represented as the same 
with Myrtilus, son of Mercury by Phaetusa, and 
charioteer to iEnomaus, king of Pisa. He was 
famous for his great address in driving, and the 
management of horses ; but his infidelity to his 
master cost him his life. He was, however, made 
a constellation after death, in compliment to his 
father, Mercury. 



Taurus — The Bull. 
The most remarkable stars in this constellation 

are: 

a Aldebaran or Palilicium. 
j8 JVath. 
y Hyadum I. 
S Hyadum II. 
s Mn. 
a is a star of the first magnitude in the right 
eye of the Bull ; hence it is sometimes called the 
Bull's Eye ; it may be known by its faint reddish 
light; [3 is in the extremity of the northern horn; 
7 is over the mouth, and e in the left eye. In the 
end of the southern horn is the star g. 

The stars a, 7, 6, s and G, form a figure like the 
letter V. This cluster of stars on the head of the 
Bull is called the Hyades. (See PI. XVI. Fig. 13). 
There is another group on the neck of the Bull, 
smaller but more dense than the former, called the 
Pleiades or Seven Stars. This is probably the 



THE CONSTELLATIONS. 75 

most remarkable and most generally known of all 
the groups in the heavens. It occupies a space 
about 2° in diameter, and contains one star of the 
4th, six of the 5th, five of the 6th, and thirty-two 
of the 7th magnitude, besides many smaller ones. 
The most important of these stars are : 
b Electra. 
d Merope. 
y\ Alcyone. 
f Atlas. 

(See PL XVI. Fig. 12). 

Six of these stars only are visible to the naked 
eye; but Pliny, Hipparchus, Ptolemy and others, 
reckoned seven. They pass vertically over the 
desert parts of Africa, Arabia, Bengal, the southern 
parts of China, California, and the Straits of Flo- 
rida, 

Among the double stars in the Pleiades, we notice : 
9j or Jllcyone. Its components are of the 4th and 7th magni- 
tude; the greater is greenish white, the smaller white; 

distant 117". 
f or Mas, of the 5th and 7th magnitudes ; distant \ second. 

This star appears double only in choice telescopes, in clear 

weather. The two stars appear to have a short period of 

revolution round each other. 
n P'eiadum, of the 7th and 10th magnitudes; very white; 

distant 3". 

In R. A. 51° 2', Dec. 23° 53', is a triple star, 7 Tauri, of. 
the 7th, 7th and 10th magnitudes, of a yellowish colour. The 
first two are two-thirds of a second apart, the third is distant 
22". 

In R. A. 81° 0', Dec. 21° 53', is a beautiful elliptical ne- 
bula, 4' long and 3' wide. 



76 THE CONSTELLATIONS. 

FABLE. 

Taurus. — The ancient mycologists pretended 
that Taurus was the bull under whose form Jupi- 
ter concealed himself, when he carried off Europa 
from Tyre, across the seas to Crete ; and that Ju- 
piter rewarded the brute's service by making him 
a constellation. The character ( y ) is said to 
represent the bull's face and horns. 

The Pleiades, or Seven Stars, derive their name, 
according to the mythologists, from the seven 
daughters of Atlas and Pleione, who were changed 
into stars. Six of them had married immortal 
gods ; but the seventh, Merope, married Sisyphus, 
a mortal, whence her light was dim and sometimes 
scarcely to be seen. The time of their rising, 
which is in the spring, was preferred by the an- 
cients for undertaking long voyages. 

The Hyades, in the south eye of Taurus, are, 
according to the mythologists, the seven daughters 
of Atlas and iEthra, and were metamorphosed into 
stars for immoderately bewailing the death of their 
brother Hyas, who had been devoured by a lion. 
The sun enters Taurus about the 20th of April. 



Cancer — The Crab, 
Contains but few important stars. The prin- 
cipal are : 

a Sertan, or Ezzaban. 
y The Northern Asellus. 
6 The Southern Asellus. 



THE CONSTELLATIONS. 77 

Between y and d is Prcesepe, or the Manger. 
This Manger (R. A. 127° 15', Dec. 20° 30) is a 

group of many stars clustered together. Upon a 
surface of about one-half a degree square, there 
are more than forty conspicuous stars, besides 
many other smaller ones. (See PI. XVI., Fig. 14). 

Among the double and multiple stars are, 

5 in the tail of the Crab ; triple ; components of the 5th, 
6th and 6th magnitudes ; all yellow. Distance of the first 
and second 1", that of the third 5". The first pair revolve 
round each other in 59 years, in an orbit nearly circular ; 
their mean distance is 1". The third revolves more slowly 
round the common centre of the other two. Or, more pro- 
perly speaking, this system is composed of three suns, 
which all revolve round a common centre. This is the 
most remarkable system in the heavens. 

t 2 is a double star, both of the 6th magnitude; distance I J"; 
the greater yellow, the smaller bluish. 
In R. A. 129° 30', Dec. 13° 13', is a dense cluster of many 

small stars, in the middle of which there is a large central 

star. 

FABLE. 

Cancer. — When Hercules, say the fabulists, 
was combating with the Lernaean Hydra, Juno, 
his inveterate enemy, sent a crab to bite him ; the 
hero, however, crushed the reptile under his heel, 
and the goddess, out of compassion, placed it 
among the constellations. The character (o), 
pointing both ways, is supposed to indicate the 
sun's declination from north to south ; but it is 
more probably only a careless imitation of the old 
Egyptian and Hindoo mark 3 for the Scarabeus, 



78 THE CONSTELLATIONS. 

or Beetle, which seems to have been the original 
sign of this constellation. The figure of a crab, 
which always moves sideways, is also fancied to 
be emblematical of the sun's motion when it en- 
ters Cancer, for it then passes sideways along the 
tropic without crossing it. Other figures, besides 
the crab, have been used for this constellation by 
the ancients ; as the beetle, and Hermanubis, or 
Hermes with the head of an ibis, among the Egyp- 
tians; the beetle, in the Hindoo zodiac; and two 
asses by the Orientalists. The Greeks, through 
whom we have received the sign, placed two asses 
in it, where they still remain, under the titles of 
Asellus Boreas and Asellus Australis ; and near 
them is the asterism Praesepe, or the Manger. The 
sun enters Cancer about the 21st of June. 



Orion. 
This is the most beautiful constellation in the 
heavens. It was known in the most ancient times. 
It is mentioned by Job and by Homer. The prin- 
cipal stars are : 

a Betel geuse. 6 Mint oka. 

|3 Rigel. s Anilam. 

y Bellatrix. £ Anitak. 

a, or Betelgeuse, is on the right shoulder, /3, or 
Rigel, is on the left foot, and y on the left shoul- 
der. Midway between a and f3 are the three stars 
in the girdle ; 8, or Mintaka, s, or Anilam, and £, 
or Anitak, standing in a right line, and forming 



THE CONSTELLATIONS. 79 

Jacob's Staff, or the Three Kings, as they are called 
by some; they are also by some denominated the 
Rake, x forms with a, y and /3, a large quadrila- 
teral figure, with Jacob's Staff in its centre. Be- 
low the three stars in the girdle are r\ and i, and 
several smaller stars, forming the sword. A little 
above the line, joining the stars in the shoulders, 
are three small stars in the head of Orion. East 
of Bellatrix are several small stars in Orion's 
shield, forming a curve, concave towards his head. 

South of £, the lowest of the three stars in the 
girdle, is <r, which Schroter considered tw T elve-fold, 
but Struve, with the Dorpat Refractor, has found 
to be sixteen-fold. Under tf, in a right line with 
£ and tf, near 6, is found the great and remarkable 
nebula ; and in the densest part of this nebula 
appears the star & itself, as a sextuple star, of 
which, however, only 4 stars, forming a trapezium, 
can be seen in ordinary telescopes. A fifth star, 
of the 11th magnitude, was discovered by Struve, 
in 1826. This small star can be seen in the 9 feet 
Fraunhofer Refractor of the High School, at Phi- 
ladelphia. A 6th star, of the 12th magnitude, has 
since been discovered. It was too faint to be 
measured in the Dorpat Refractor; but in the 
great Pulkovah Refractor its place is readily mea- 
sured, with the field of the telescope illuminated. 

By comparison of the recent drawings of this 
nebula with the more ancient, it appears that it 
is continually changing its appearance. Perhaps 
it is undergoing the process of condensation, sup- 



80 THE CONSTELLATIONS. 






posed by some astronomers to take place in the 
formation of stars and stellar systems ! 

Among the double stars we also remark, 

/3 or Rigel ; its components are of the 1st and 8th magni- 
tudes; distant 10"; colour yellowish white. See Plate 
XVI. 

£ in Jacob's Staff, of the 2d and 6th magnitudes ; distant 
2" ; the greater yellowish white, the smaller reddish green. 

i of the 3d and 7th magnitudes ; distant 1 \" ; the greater 
yellowish white, the smaller blue. 

% is a triple star, of the 4th, 6th and 12th magnitudes ; dis- 
tances 4", and. 27" ; the greatest yellowish, the smaller 
purple. 

g of the 5th and 8th magnitudes ; distant 7" ; yellow and 
blue. 
In R. A. 82° 0', Dec. 1° 19', near s, and southward from 

it, is a beautiful star, in a very large round nebula of 24' dia- 
meter. 

This constellation abounds in nebulous stars, 
which are quite variable in their nebulosity. Her- 
schel, the elder, attributes this change to the 
changes that seem to be going on in the nebula) in 
Orion, which he thinks are situated on this sid«j 
of the stars, and cause their nebulous appear- 
ance. 

FABLE. 

Orion was a celebrated hero of antiquity, and 
a mighty hunter, who accompanied Diana and 
Latona to the chase, but perished by the bite of a 
scorpion for his improper conduct. Being, how- 
ever, a descendant of the gods, Jupiter made him 
a constellation ; and he is represented with a 



THE CONSTELLATIONS. 81 

sword in his belt, a lion's skin upon his left arm 
as a shield, and a club in his right hand. He 
seems to be the representative of Nimrod, that 
"mighty hunter," who is supposed to have been 
the author of the postdiluvian heresy. 



Gemini — The Twins. 

This constellation is readily distinguished by 
the two stars, 
x a, or Castor. 

j3, or Pollux. 

inline drawn from (3 through a of Orion, and 
prolonged north-east of a to nearly twice the dis- 
tance of these two stars, will terminate near (3 in 
the head of Pollux. Below, and near this line, 
lie y, r ( and 6, three stars of the 3d magnitude, of 
w T hich the first is in the foot, the second in the 
thigh, and the third in the girdle of Pollux. 
About 4|° north-west of Pollux, is a or Castor, in 
the head of Castor. A line drawn through a, 
parallel to the former line, would pass through s 
in the knee, and just below ^ in the foot of Cas- 
tor ; these two stars are also of the 3d magnitude. 
Besides the seven principal stars above-mentioned, 
there are a great many smaller ones, which may 
be found by means of their positions with refer- 
ence to the above and to each other. 



82 THE CONSTELLATIONS. 

Among the double stars are, 
a or Castor; its components are of the 3d and 4th magni- 
tudes ; both greenish; distant 5". The stars of this re- 
markable and beautiful pair revolve round each other in 
232 years ; their mean distance is 7". They may be seen 
double in a good three feet telescope; they have both the 
same proper motion among the other stars of 119" in a 
century. See Plate XVI. 
8 of the 3d and 8th magnitudes ; distant 7" ; the greater yel- 
lowish, the smaller purplish. 
t of the 3d and 10th magnitudes; distant 10''; the greater 
bluish green. 

In R. A. 108° 45', Dec. 29° 50', stand two spherical nebulae 
of equal magnitudes, with their limbs in contact, each having 
a bright nucleus in the centre. 

In R. A. 109° 46', Dec. 21° 15', is a star of the 8th mag- 
nitude, in the centre of a round, light nebula, of 25" dia- 
meter. 

FABLE. 

Gemini. — The mythologists pretend that Castor 
was the son of Jupiter and Leda; and that be- 
tween him and his half-brother Pollux immortality- 
was alternately shared. The character of this 
sign (n) is two perpendicular lines, joined at top 
and bottom by two parallel lines, indicative of 
union. The figure has long been that of two 
boys ; but it has had other devices, as two goats, 
&c. The sun enters Gemini about the 21st of 
May. 



Monoceros — The Unicorn. 
This constellation was introduced by Hevelius. 
It occupies a considerable space south of the 



THE CONSTELLATIONS. 83 

Twins and the Little Dog, and east of Orion. It 
contains only four stars of the 4th magnitude, and 
some others still smaller, and is not very easily 
traced in the heavens. 

In R. A. 95° 5', Dec. south 6° 55', is a triple star, whose 
components are of the 5th, 5th and 6th magnitudes ; distant 
2" and 7" ; all white. 



Canis Minor — The Little Dog. 
This constellation is distinguished by two large 
stars, 

a Procyon, 

(3 Mirza or Gomeiza, 

which lie about 20° south of Castor and Pollux. 
Procyon is a very bright star of the 1st magni- 
tude : it forms, with (3 and y of the Twins, a tri- 
angle very nearly equilateral. 

FABLE. 

Canis Minor. — This constellation is feigned to 
have been a hound of Orion by the Greeks ; or, 
according to some, it was Msera, who, by his 
cries, showed Erigone where her murdered father 
had been thrown — then pined away, but was 
made a constellation. The Egyptians were pro- 
bably the inventors of this constellation ; and they 
may have given it this figure to express a little 
dog, or watchful animal, going before or leading 
on the greater, or rising before it ; and hence the 
Latins called it Antecanis, the star before the dog. 



84 THE CONSTELLATIONS, 

PLATE VII, 
CONSTELLATIONS. 

Bootes The Herdsman. 

Lyra The Harp. 

Hercules .... Hercules. 

Corona Borealis . . The Northern Crown. 

Taurus Poniatowski The Polish Bull. 



Bootes — The Herdsman. 
This is a large constellation, south of the Great 
Bear, and between the Heart of Charles and the 
Northern Crown. The principal stars are: 
a Arcturus. v\ Mufried. 

6 Kekkar. /x Alkalurops. 

s Izar. 

Arcturus is a bright star of the 1st magnitude, 
and may be found by conceiving the curve which 
passes through the three stars in the tail of the 
Great Bear to be continued about 30° from rj. On 
the opposite sides of Arcturus, and nearly in a 
line with it, are two stars, r\ and g, of the 3d mag- 
nitude, in the legs. 6° east of r\ of the Great Bear, 
is 6 in the left hand. A line drawn through S and 
y\ of the Great Bear, and produced twice their 
distance beyond tj, would terminate near y in the 
left shoulder; and about 6° east of this star w 7 ill 
be found /3 in the head of Bootes. About 8° below 
j3, and in a line with d, is 6 in the right shoulder. 



THE CONSTELLATIONS. 85 

y, /3 and 8, form a triangle, right angled at (3. In 
a line with 8 and Arcturus, and midway between 
them, is s in the belt. 

The principal double stars in this constellation are : 
c in the girdle. Its components are of the 3d and 6th mag- 
nitudes ; distant 4" ; the greater deep yellow, and the 

smaller bluish green. It requires a good telescope to 

show € as a double star. 
J not far from re ; 4th magnitude ; distant 1|" ; both white, 
i a triple star, of the 6th, 6th and 7th magnitudes ; the two 

greater distant J of a second, the smaller distant 38". 
X on the left hand ; 5th and 8th magnitudes ; distant 13" ; the 

greater white, the smaller reddish blue. 
H on the right calf; 5th and 6th magnitudes; distant 1" \ 

both very white. 
| in the right knee; 5th and 7th magnitudes; distant 9'; 

the greater yellow, the smaller purple. They revolve 

about each other in a period of 120 years. 

We find, moreover, in thw constellation, the following 
objects : 

In R. A. 196° 0', Dec. 19° 4', a beautiful, round group of 
stars, of 5' diameter, which, in the middle, is very bright. 

In R. A. 209° 30', Dec. 29° 20', a large, round, very rich 
group, of 10' diameter, without a light nucleus. 

In R. A. 224° 45', Dec. 19° 6', a very large, round, plane- 
tary nebula, of 6' diameter : and 

In R. A. 225° 0', Dec. 20° 32', two equal, oval nebulae, 
nearly touching each other. 

FABLE. 

Some suppose Bootes to be the same with Ica- 
rus, the father of Erigone, who was killed by 
shepherds for inebriating them. Others maintain 
that, before his translation, he was Arcos, the son 

7 



Ob THE CONSTELLATIONS. 

of Jupiter and Calisto; others, that he was Ly- 
caon, the father of Calisto; and some hold him to 
be the same with Erichthonius, the inventor of 
chariots and the method of harnessing horses to 
them. This, however, confounds him with Auriga. 
The fact is, these are all ideal personages; and 
the origin of this constellation seems to be lost in 
antiquity. Bootes is represented as in a walking 
attitude, grasping in his right hand a spear, while 
in his left, extended upwards, he holds the last of 
the dogs Asterion and Chara, which seem to be 
barking at the Great Bear. 



Lyra — The Harp. 
This small, but beautiful constellation, lies in 
one of the regions richest in stars of all the hea- 
vens, where also the milky-way is very bright. 
a or Vega, also called Lucida Lyrce, is one of the 
largest and most beautiful of the fixed stars. The 
other large stars are /3 or Sheliac, and y or Sula- 
phat. This constellation lies south-east of the head 
of the Dragon, and west of the neck of the Swan. 
Vega forms, with two small stars, s and £, an equi- 
lateral triangle, ft, y and (5, may be easily recog- 
nised in the heavens by an inspection of the map. 

Among the double and multiple stars are the following : 
a Its principal component is of the 1st magnitude. It has 
a very small companion of the 11th magnitude placed at a 
distance of 42". (See PI. XVI. Fig. 11.) This system 
is distant from our sun 771,400 times the earth's mean dis- 
tance. Its light reaches us in 12 years. 



THE CONSTELLATIONS. 87 

3 is a quadruple star, or two pairs of stars, standing near 
each other. Both pairs may be seen in the same field of 
the telescope. The stars are of the 3d, 7th and 9th mag- 
nitudes, and the greatest j3 is changeable in its light. It 
diminishes in 6J days from the 3d to the 5th magnitude, 
and then increases again to the 3d. 

e over Vega ; 5th and 6th magnitudes ; distant 3" ; the greater 
greenish white, the smaller bluish white. Near this also 
is a second double star, visible in the same field of the tele- 
scope, both white, of the 5th magnitude, distant 2J". 
Both these pairs of stars have the same proper motion of 
8" in a century. 

f on the left of Vega and near it; 4th and 5th magnitudes; 
distant 44" ; both greenish white. This star appears dou- 
ble with ordinary telescopes. 

y on the left side of the Harp ; 4th and 8th magnitudes ; dis- 
tant 28" ; the greater blue, the smaller ash-coloured. 
In this constellation we also find, 
In R. A. 287° 30', Dec. 29° 53', a beautiful group or cluster 

of stars, nearly in the figure of a triangle, without any proper 

nucleus. The greatest diameter of the triangle is 3' : 

In R. A. 281° 45', Dec. 32° 49', between ]3 and y, a very 

remarkable annular nebula, whose exterior diameter is 6 J". 

(See Plate XVIII. Fig. 48). 

FABLE. 

Lyra. — This celestial lyre is said to be the 
same which Apollo gave to Orpheus, when the 
latter descended to Pluto's dominions to redeem 
his bride Euridice from death; and after his own 
decease, it was made a constellation. It is with 
much greater propriety supposed to be an emblem 
of the very ancient doctrine of the musical har- 
mony of the spheres, which still prevails in the 
East. 



88 THE CONSTELLATIONS. 



I 



( Hercules et Cerberus — Hercules with the Cer- 

i berus. 

In this constellation we observe a or Ras Al- 
gethi, on the head ; u or Kajarn, on the right 
elbow; and X or Masini, in the upper part of the 
left arm : — a in the head, 6 in the breast, and * in 
the leg, are equidistant, and in a right line, which 
produced would pass through the North Pole. 
Extending from S towards y in the Harp, is a line 
of several small stars in the left arm, and below 
this arm are several small stars in the Cerberus. 
The star \ forms a nearly equilateral triangle 
with 6 and at, and near the centre of this triangle 
is s. About midway between Ras Algethi and 
the Northern Crown, is /3; and 2° south-west of /3 
is y. These stars are chiefly of the 3d magnitude. 
Several others of the 3d and 4th magnitudes may 
readily be traced by a reference to the map. 

Among the remarkable double stars of this constellation, 

are found 

a Its components are of the 3d and 7th magnitudes ; distant 
5" ; deep yellow, and deep blue. The greater changes from 
the 3d to the 4th magnitude in 60 days. (See PI. XVI.) 

b of the 3d and 8th magnitudes ^ 25" apart ; the greater green, 
the smaller ash-white. 

I of the 3d and 6th magnitudes ; distant 1" ; the greater yel- 
lowish, the smaller purplish. They revolve round each 
other in 31 years, at a mean distance of 1^ seconds. 

X of the 5th and 6th magnitudes; distant 31"; both yellow; 
easily seen in common telescopes. 

fi of the 4th and 10th magnitudes ; yellow; 30" apart. The 



THE CONSTELLATIONS. 89 

proper motion of these two stars among the other stars, is 

82" in a century. 
£ of the 4th and 5th magnitudes ; distant 4" ; greenish white, 

and green. 

In R. A. 248° 45', Dec. 36° 48', between ? and j?, is a very 
rich group of stars of an irregular form, without nucleus. 

This is the constellation towards which our sun 
with all its planets and their satellites, is moving 
in absolute space. The elder Herschel first con- 
ceived the idea of explaining the proper motions 
of the stars by such a supposition. He chose for 
the point of direction the star X. Herschel's 
opinion was doubted by many astronomers ; but 
was finally shown to be correct by Argelander. 
It is now ascertained that our system is moving 
towards a point in R. A. 259°, Dec. 35°, which is 
about a degree north-east of the small star u Her- 
culis, being within 10° of the point first conjec- 
tured by Herschel. The velocity of our system 
in this direction is estimated, by Struve, to be 
about half as great as that of our earth in its 
orbit, or about 8 miles per second. 

FABLE. 

Hercules, who is represented in this plate as 
kneeling, with the skin of the Lernaean lion thrown 
over his shoulders, holding a club in his right hand, 
and Cerberus in the left, was a celebrated hero of 
the most remote antiquity, and one of the great gods 
of the Egyptians. Many persons are said to have 
borne the name ; but all their exploits are attri- 
buted to the Theban Hercules, the reputed son of 



90 THE CONSTELLATIONS. 

Jupiter and Alcmene. Of his numerous achieve- 
ments, twelve are more particularly noticed as 
the Twelve Labours of Hercules, and are supposed 
to be emblematic of the sun's progress through 
the twelve signs of the zodiac. The name is a 
corruption of Arcles, a title of the sun. 

Cerberus, according toHesiod, was a dog with 
a hundred heads, though our mythologists give 
him only three ; he was reputed to belong to 
Pluto, and to be stationed at the gates of the infer- 
nal regions as a guard. Cerberus is represented in 
the plate as a three-headed serpent. From this 
situation, Hercules, as his concluding labour, drag- 
ged him up to the realms of day, when he went to 
redeem Alceste. Some suppose this to be an astro- 
nomical fable, relating to the sun on his arrival at 
the autumnal equinox. 



Corona Borealis — The Northern Crown. 
This beautiful little constellation is situated 
between Bootes and Hercules. The two largest 
stars of this constellation are a, or Gemma, the 
Jewel, and /3, or Nusakan. This constellation 
may be easily recognised by the regular curve 
formed by the principal stars. 

The principal double stars are, 
y Its components are of the 4th and 7th magnitudes ; dis- 
tance, in 1826, T y, in 1833, T 4 /, in 1841, £", in 1842, round 
and single ; the greater greenish white, the smaller purple, 
g of the 4th and 5th magnitudes; distant 7"; the greater 
greenish white, the smaller greenish. 



THE CONSTELLATIONS. 91 

17 of the 5th and 6th magnitudes; distant 1"; both yellow. 
They revolve round each other in 43 years. Their proper 
motion among the stars is 22" in a century. 
$ of the 5th and 6th magnitudes; distant 1". They revolve 
round each other in 608 years, and their mean distance is 
4". Their doubleness can only be detected by good tele- 
scopes. They have both the same proper motion of 31" in 
a century. 
In R. A. 227° 44', Dec. 27° 30', are two very white stars, of 

the 6th magnitude ; distant lyV'. 
v a triple star, of the 7th, 9th and 10th magnitudes ; dis- 
tances 89", and 126". 

In R. A. 235° 5', Dec. 28° 47', over S, is a changeable star, 
which, in the period of 335 days, from being of the 6th mag- 
nitude, entirely disappears, and again increases to the 5th. 

FABLE. 

Corona Borealis. — This crown has the repu- 
tation of being the same which Bacchus gave to 
Ariadne, the daughter of Minos; and after her 
death it was made a constellation; from Gnossus, 
a city of Crete, and the residence of Minos, it has 
obtained the name of the Gnossian Crown. By 
the Hebrews this asterism was called Ataroth, 
which is still its name in the East. 



Taurus Poniatowski — The Polish Bull, 

Is between the head of Hercules and Lyra, 
was introduced in the year 1778, by the Polish 
astronomer Poczubut, in honour of the King of 
Poland, and contains only stars of the 4th and 
smaller magnitudes. 



92 THE CONSTELLATIONS. 

PLATE VIII. 
CONSTE LLATIONS. 

Leo Major . . . The Great Lion. 

Virgo .... The Virgin. 

Coma Berenices . Berenice's Hair. 

Sextans .... The Sextant 



Leo Major — The Great Lion. 
The principal stars in this constellation are : 

a, or Regulus. 

(3, or Denebola. 

y 9 or Algieba. 

8, or Zosma, also Hur el Asad. 

s, or the southern Ras el Asad. 

fju, or the northern Ras el Asad. 

x, or Minchir. 

o, or Coxa, also called Lubra. 
A line drawn from <5 through y of the Great 
Bear, will point to Regulus, in the breast, some- 
times called the Lion 9 s Heart, and would also pass 
through y, in the neck of the Lion. v\ below y, 
and y, £, /x and s, form a curve in the head and 
neck ; and these, with Regulus, constitute a figure 
somewhat like a sickle, Regulus and rj forming the 
handle. In a line with Regulus and Arcturus, 
will be found /3, or Denebola, a star of the 2d 
magnitude, in the tail of the Lion. Nearly in a 
line with /3 and y is 6; and 5° due north of A is S; 
and a line drawn from S through 6, would point 
out several smaller stars in the hinder legs. 



THE CONSTELLATIONS. VO 

Of the most conspicuous double stars of this constellation 
we remark : 

y the most splendid double star in the northern hemisphere, 
whose components are of the 2d and 4th magnitudes ; dis- 
tant 3" ; the greater gold yellow, the smaller greenish pur- 
ple. Both stars have the same proper motion of 31" in a 
century among the other stars. (See Plate XVI. Fig. 5.) 
i of the 4th and 7th magnitudes ; distant 2" ; the greater 

yellowish, the smaller blue. 
t» on the fore-paw ; of the 5th and 7th magnitudes ; both yel- 
low. They revolve round each other in 83 years, and their 
mean distance is |". In 1841, their distance was T y; 
since then, in 1842 and 1843, they have appeared as a 
single round star. 

In R. A. 116° 30', Dec. 25° 42', there is a beautiful, well- 
defined double star, of the 5th and 7th magnitudes ; dis- 
tant 7". 

In R. A. 144° 12', Dec. 12° 21', between the fore-paws, is 
a variable star, which, in a period of 311 days, fades from the 
5th magnitude and disappears, and again reappears and in- 
creases to the 5th magnitude. 

The most remarkable nebulae of this constellation are : 
In R. A. 167° 30', Dec. 14° 0', a light round nebula, grow- 
ing brighter toward the middle, with a decided nucleus. 

In R. A. 140° 30', Dec. 22° 15', a double nebula. Both 
nebulae together form an elliptic figure, of which the major 
axis is 3'. 

InR.A. 167° 45', Dec. 14° 32', a nebulous streak 15' in 
length and 1' in width, brighter toward the middle, with a 
fine star. 

There is, also, in R. A. 181° 45', Dec. 14° 6', a nearly 
similar, though smaller nebula. 

FABLE. 

Leo. — This sign is supposed by the fabulists to 
be a metamorphosis of the Nemaean lion, which 



94 THE CONSTELLATIONS. 

Hercules slew. The character (SI) represents the 
tail of that animal in an agitated state. In the 
Egyptian calendar, the sign Leo contains the 
figures of two lions, and the head of a third. 

The sun enters this sign about the 23d of July. 
It is chiefly situated north of the ecliptic, and 
passes over the countries situated in the north part 
of the torrid zone, where lions are generally found. 



Virgo — The Virgin. 

a or Spica, the Ear of Corn, or Azimech. 

/3 or Savijava. 

e or Vindemiatrix. 

r\ or Zaniah. 
Spica is a beautiful star of the 1st magnitude, 
and may be easily distinguished by its brilliancy, 
being the only conspicuous star in the neighbour- 
hood. A line drawn from /3 in the head of Bootes 
through Arcturus, will point it out. Spica, Arc- 
turus, and /3 in the tail of the Lion, form a very 
nearly equilateral triangle, the sides of which are 
each about 40°. A line drawn from Arcturus 
between q and u of Bootes, will point out s in the 
northern, and /3 in the southern wing of the Vir- 
gin. A line drawn from (3 to a point about 5° 
north of Spica, will pass q s y and 6, all in the 
southern wing; this line continued, will show us 
x and X in the southern foot. A little north of 
these last we find p in the northern foot, and <p 
and i in the robe. Between s and y is 5 in the 



THE CONSTELLATIONS. 



95 



waist. The head is marked by four small stars 
between (3 Virginis and /3 in the tail of the Lion. 



The Stellar System y Virginis. 

The appearance of the two components of this 
system in the Dorpat telescope, is shown in the 
cuts. Both are of the 3d magnitude, of a yellow- 
ish colour. 



1833, 16th May. 



1835, 2d May. 




1835, 20th May. 



1836, 3d June. 




This drawing is for an inverting telescope, 
magnifying the distance 1000 times. The upper 
star in the figure is variable in size compared 



96 THE CONSTELLATIONS. 

with the other. Sometimes it is larger, sometimes 
it is smaller. Mr. Maedler explains this variation 
by supposing that one of them, though apparently 
single in the best telescopes, is really a double 
star, forming in this way a triple system. A pair 
of stars so close to each other in this system must, 
according to Kepler's third law, " that the squares 
of the periodical times are as the cubes of the 
mean distances/' revolve rapidly round each other, 
and cause a change in the apparent size perhaps 
as great as that which Struve has noticed. The 
disturbance of the two bodies by their near ap- 
proach to the third, must be very great. 

EXPLANATION OF THE DRAWING OF THE APPARENT 
ORBIT. 

Maedler has collected together all the measures 
of the bearing and distance of the components. 
The earliest, in 1719, is a measure of the bearing 
by Bradley. The distance by Cassini, in 1721, is 
only a vague estimate. The bearings and dis- 
tances by Mayer in 1756, and the elder Herschel 
in 1781 and 1803, are more precise. The mea- 
sures made since 1825 with the Fraunhofer filar- 
micrometer, chiefly by Struve and Maedler, ex- 
hibit great perfection, and conform well with 
each other. That of 1844, was made in Februa- 
ry, at the High School observatory. These mea- 
sures are all represented in the drawing. Brad- 
ley's, Mayer's, and the elder Herschel's bearings, 
are retained. Cassini's distance has been dimin- 




Stellar System. Gamma Virginis. 



THE CONSTELLATIONS. 97 

ished about a second, and applied to Bradley's 
bearing. The distances of Mayer and the elder 
Herschel have been slightly modified, so as to con- 
form to the most natural curve. This apparent 
curve is an ellipse, the plane of which is perpen- 
dicular to the line of direction, leading from the 
observer to this stellar system. The true orbit is 
inclined to this apparent orbit, and, of course, is 
here seen in perspective. 

The earliest computation of the orbit of these 
two stars was made about 15 years since, by Sir 
John Herschel, before their passage of their peri- 
helion. The imperfection of the measures then 
available, was such as to lead to an orbit with a 
period of 560 years. Shortly after the perihelion 
passage, and the opening of the stars in 1838, Mr. 
E. P. Mason, of Yale College, obtained an orbit 
with a period of 171 years. Maedler, from the 
most recent measures compared with all the pre- 
ceding, finds an orbit for these two components, 
having a period of 145f years. According to him, 
they revolve round each other in an elliptic orbit, 
having for the longer axis G.to", and for the 
shorter only T 3 F of a second. The history of this 
stellar system extends back 125 years, in which 
period they have nearly completed their orbit, 
having passed their greatest distance or aphelion 
in 1763, and their perihelion or nearest approach 
in 1836. 

At this time the components were so close that 
no telescope in the world could separate them. 



98 THE CONSTELLATIONS. 

Their appearance, when magnified a thousand 
times in the Dorpat telescope, is shown above. 
In the spring of 1836, their angular motion was 
a degree in 5 days. Such a velocity was required 
in-order that, according to Kepler's second law. 
their radius vector, or the line joining them, should 
sweep through the same area in a day as when at 
their greatest distance in 1763. 

This remarkable 'stellar system promises to 
afford a deep insight into the secret workings of 
nature. The orbit of Msedler was computed sim- 
ply on Kepler's hypothesis of an ellipse, in which 
equal areas are described in equal times. 

If the force which causes this motion is that of 
Newtonian, or universal gravitation ; then the ac- 
tual velocity of each component in its orbit must 
increase as the square of their observed distance, 
or radius vector, diminishes. Maedler having com- 
puted their orbit without the latter supposition, 
found that the employment of it would cause no 
sensible change in the result ; a beautiful con- 
firmation this of the doctrine of the universality 
of Newtonian gravitation ! 

The components of this system, besides their 
orbital motion caused by some original projectile 
force, and their mutual attractions, have also the 
same proper motion of 52" in a century, among 
the other stars. This affords a farther proof that 
they are bound together by some force different 
from that which connects them with the stars that 
appear in their vicinity. 



THE CONSTELLATIONS. 99 

Their distance will increase for the rest of the 
19th century. In the latter portion of it they 
will be easily seen double in ordinary telescopes. 
At present their distance is 2". They appear 
elongated in the 9 feet telescope of the High School 
Observatory, with a power of 100. With a power 
of 500, they appear to be separated by an inter- 
val five times as great as the diameter of the disc 
of either. 

The other principal double stars are, 
at the left of y ; its components are of the 4th and 9th mag- 
nitudes ; distant 7" ; both white. 
$ of the 5th and 10th magnitudes; yellow ; distant 4". 

In R. A. 213° 30', Dec. 9° 13' ; of the 5th and 7th magni- 
tudes ; distant 6" ; the greater bluish white, the smaller 
greenish white. 

The star in R. A. 187° 5', Dec. 8° 5', on the right wing of the 
Virgin, is variable. In the period of 145 days it varies from 
the 6th magnitude to invisibility, and increases again to the 6th. 

In R. A. 181° 15', Dec. 15° 51', is found a narrow nebula, 
nearly 10' in length, irregular at one end, with a nucleus like 
a bright star in the middle. 

In R. A. 154° 0', Dec. 5° 53', there is a star of the 8th 
magnitude, with a spherical, bright atmosphere, which is 
visible with moderate telescopes. 

In R. A. 193° 0', Dec. 3° 25', a star of the 8th magnitude, 
on one side of which hangs a small oval nebula. 

In R. A. 187° 45', Dec. 10° 40', south ; a bright, oval ne- 
bula, 5' long, and §' wide, with a light nucleus. 

FABLE. 

Virgo. — This constellation, among the myco- 
logists, was Astraea, the goddess of Justice, who 
dwelt upon earth during the golden age, but was 



100 THE CONSTELLATIONS. 

translated to heaven when men gave themselves 
up to wickedness. Originally the character of 
this sign (tik) consisted of three ears of corn ; the 
figure is that of a virgin, with a stern but majestic 
countenance, and winged, holding a pair of scales 
in one hand and a sword in the other; or with a 
palm-branch in one hand and some ears of corn 
in the other. Among the Egyptians, Virgo was 
the goddess Isis ; in the Oriental zodiacs, she is 
represented as a mother; the Arabian and Syrian 
astronomers describe her w 7 ith a male infant in 
her arms; and in the Persian sphere she also 
nurses a boy. The sun enters the Virgin about 
the 23d of August. 



Coma Berenices — Berenice's Locks. 

This is a cluster of small stars about midway 
between Denobola, in the Lion, and a, or Charles' 
Heart, in the Hounds. It contains five stars of 
the 4th magnitude, with many smaller ones. Its 
appearance to the naked eye is the same as that 
of a resolvable nebula in a good telescope. 

The cut shows the appearance of 42 Berenice's 
Locks in the Dorpat telescope, with a magnifying 
power of 1000. 

1835, 4th June. 1836 29th May. 




THE CONSTELLATIONS. 101 

This pair is situated in R. A. 195° 24', Dec. 18° 
28' ; both yellow ; of the 6th magnitude. In 1827 
they were distant J"; in 1841, ^" ; in 1843 they 
appeared single and round. They have both the 
same proper motion among the stars, 45" in a cen- 
tury. 

The principal double stars are, 

In R. A. 178° 45', Dec. 22° 26', at the right of the star h, 
is a double star, whose components are both of the 7th mag- 
nitude ; distant 4" ; having a beautiful well-defined image. 

In R. A. 186° 30', Dec. 19° 21', near the star 1, of the 5th 
and 6th magnitudes; distant 21"; the greater yellow, the 
smaller blue. 

In R. A. 191° 12', Dec. 22° 11', there is a triple star of the 
5th, 8th and 9th magnitudes; the greatest yellowish, the 
middle-sized blue ; distances 1J" and 29". 

In R. A. 186° 8' Dec. 22° 9', is a pair of stars of the 8th 
and 9th magnitudes. In 1827, they were §" apart; in 1841, 
they appeared single and round ; in 1842, they were again 
parted to the distance of J". 

In R. A. 187° 0', Dec. 12° 8', is seen a very beautiful 
double nebula; both nebulas bright, rounded, and lighter 
toward the centre. Their diameters are 45" and 60". 

In R. A. 192° 0', Dec. 22° 37', lies a double star enclosed 
by a bright, round nebula, whose diameter is nearly 6'. 

In R. A. 187° 0', Dec. 26° 56', we find a nebulous streak, 
15' in length and £' wide, with a faint nucleus, and in the 
middle of it a star of the 9th magnitude. Parallel to this 
nebula and near to it, another similar, but smaller nebula is 
visible. 

In R. A. 196° 0', Dec. 19° 4', between the stars r and v, 
appears a very rich and dense cluster of stars, of the 10th 
and 12th magnitudes. The diameter of the cluster is 5'. 
8 



102 THE CONSTELLATIONS. 

FABLE. 

Coma Berenices. — When Ptolemy Euergetes, 
king of Egypt, was going on a dangerous expedi- 
tion to Syria, about B. C. 247, his queen, Bere- 
nice, dedicated her hair to Venus, and hung it up 
in the temple. Sometime after the return of 
Euergetes, the tresses were missing ; and Conon 
of Samos, a great astronomer of his time, declared 
that Jupiter had transferred them to the heavens 
in the form of this constellation. 



Sextans — The Sextant 
This was instituted by Hevelius, and contains 
only small stars. It is situated between the Great 
Lion and the Water Serpent. 



PLATE IX. 
CONSTELLATIONS. 

Antinous Antinous. 

Aquila The Eagle. 

Libra The Scales. 

Serpens The Serpent. 

Del philips The Dolphin. 

Equiileus The Little Horse. 

Scutum Sobieski .... Sobieski's Shield. 
Turd us Solitarius .... The Solitary Thrush. 
Vulpecula et Anser . . . The Fox and Goose. 
Sagitta The Arrow. 



THE CONSTELLATIONS. 103 

Antinous — Antinoils. 

This small constellation under the Eagle was 
instituted by Tycho Brahe. It contains two stars 
of the 3d and four of the 4th magnitude, which 
may be found on referring to the map, by means 
of the stars in the Eagle. 
9i in the left arm, is variable. It changes in 7| days from the 

4th to the 5th magnitude. 
In R. A. 301° 30', Dec. 4° 2', south, is a double star, of the 

6th and 8th magnitudes ; distant 14". 



Aquila — The Eagle. 
The Eagle is situated south of the Swan. The 
principal stars are : 

a Altair. y Tarazed. 

(3 Mschain. £ Dscheneb Okab. 

This constellation may be readily found by the 
three stars a, (3 and y, placed in a line, the bright 
star a being midway between the other two. 
The two stars g and s will be found midway be- 
tween Altair and the Cerberus (in the hand of 
Hercules). In the southern wing, south-west of 
y, are the two stars p and S. 
Among the double stars we notice, 
ft about 2° N. E. of y ; its components are of the 6th and 

7th magnitudes ; distant 1". Both stars are yellow. 
X of the 6th and 7th magnitudes ; distant 1" ; lately disco- 
vered by Struve, at the Pulkovah Observatory. 
In R. A. 290° 45', Dec. 8° 53', there is a round, very rich 
group of stars, 40" in diameter. 



104 THE CONSTELLATIONS. 

Libra — The Scales. 

The Scales lie east of the Virgin. The princi- 
pal stars are : 

a Zuben el Genubi. 
f3 Zuben es Chimali. 
y Zuben el Akrab. 
a in the southern scale, may be found by con- 
tinuing the line of the stars in the southern wing 
and foot of the Virgin. /3 is north-east of a, and 
about 9° distant from it. /3, Arcturus and Spica, 
form a triangle nearly equilateral. The other 
stars may be found, by referring to the map, 
without much difficulty. 

The star % is triple ; of the 5th, 5th and 7th magnitudes ; 
distant 1" and 7" ; the two greatest yellowish white, the 
smallest bluish white. 

In R. A. 270° 30', Dec. 2° 44', is a beautiful, dense cluster 
of stars, whose centre is very bright. 

FABLE. 

This sign constitutes the balance of Astraea, and 
its character (^) is supposed to represent the 
beam. The Greeks pretend that it was placed in 
the zodiac to perpetuate the memory of Mochus, 
the reputed inventor of weights and measures. 

The sun enters Libra about the 23d of Septem- 
ber, when the autumnal equinox occurs. The 
sun, being then vertical to the equator, has no 
declination, and the days and nights are equal all 
over the earth, except at the poles, where the day 
closes at the north and opens at the south. 



THE CONSTELLATIONS. 105 

Serpentarius vel Ophiuchus — The Serpent- 
Bearer, 
The principal stars are : 

a Ras Mhague. 6 First Jed. 

/3 Celbalrai. s Second Jed. 

a, in the head, may readily be found by its near- 
ness to Ras Algethi in Hercules. South of a and on 
each side of it, are the stars /3 and x in the shoul- 
ders ; and near these are two smaller stars, y and i, 
which form with a an isosceles triangle. About 
20° below the stars in the shoulders, are y\ and £ 
in the knees, which form nearly a rectangle with 
(3 and x. The feet are marked by several small 
stars in each, below those in the knees. 

The appearance of r of the Serpent-Bearer in 
the Dorpat telescope is given in the cut. 



1835, 3 Sep. 


1836, 22 Aug. 


Wb Yam 

" S ' ■ IfMlll 









This stellar system is situated in the right arm 
of the Serpent-Bearer; the component stars are 
of the 5th and 6th magnitudes, respectively ; both 
yellow. In 1780 this system appeared double, 
though the components were very close. In 1828 
it appeared single. In 1835 the stars were seen 



106 THE CONSTELLATIONS. 

:n contact; the distance was §". In 1836 the dis- 
tance was |", and the bearing had changed about 
10°. In 1841 the distance was |". It is still a 
difficult object for the best telescopes. 

The stellar system p of the Serpent- Bearer. 
R. A. 269° 9', Dec. N. 2° 33'. 

The orbit of this remarkable system is shown 
in the figure. It has revolved nearly round since 
its first discovery by the elder Herschel in 1780. 
Its period is 93 years, being a little greater than 
that of the planet Uranus. The component 
stars are of the 7th and 8th magnitudes. The 
greater is yellow, the smaller purple. Their mean 
distance is 4}". Their present distance is 6i". 
They are now nearly at their greatest distance 
apart. They passed their perihelion in 1812. 
They have both the same proper motion of 112" 
in a century among the other stars. The orbit 
has nearly the same mean distance as y Virginis ; 
but it is less eccentric, as will be noticed by com- 
paring the drawings. 

The ellipse of p of the Serpent- Bearer is seen 
in the drawing in perspective, the true orbit being 
much inclined to the plane of the apparent orbit, 
and approaching much nearer to the shape of a 
circle than the drawing. This remarkable stellar 
system p of the Serpent- Bearer has been recom- 
mended by Bessel to the special care and atten- 
tion of astronomers, on account of the shape of its 
orbit. By measuring the bearing and distance 
of the components, as well as those of each from 



/ % 




/x, <J> 


^ 


P/fll B^' J^^ 




"IK, 


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183, fc M ,9 *i.f 


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a3 i?ni 8 ~*s 


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"*.#£?/ 


\ 

\ 
\ 


J825-6 


\ 
\ 


#1822-6 


\ 
\ 
I 


! 


1 

1 

1 


1 


1 
1 

J 
/ 
/ 
/ 


* 


/ 

/ 
/ 
/ 

/ 


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/ 
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/ 
/ 
/ 
/ 


IS. \^_ 


^& 1804 4 


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[iiiiliiiil _ 





Stellar System p of the Serpent Bearer. 



THE CONSTELLATIONS. 107 

other stars in their vicinity, not physically con- 
nected with them, astronomers will be enabled in 
time to determine the motion of each component 
with respect to their common centre, and conse- 
quently their relative masses. If the distance 
should also be found like that of 61 Cygni, we 
should then know how the mass of each compares 
with that of our sun. This system will also be 
useful in deciding the question, whether the New- 
tonian law of gravity prevails in the mutual at- 
tractions of the stars. Maedler, who has recently 
discussed this latter question, thinks that the 
known Changes of bearing and distance of these 
two stars cannot be reconciled with the doctrine 
of universal gravity, unless we suppose that the 
actual centre of gravity of each of these suns is 
different from the apparent centre as estimated in 
the telescope. Since y Virginis on the contrary 
confirms the doctrine of the universality of gravi- 
tation, and since Msedler's anomaly may be ex- 
plained, according to M. Houzeau, by the aberra- 
tion of the stars' proper motions, we have no rea- 
son to consider p of the Serpent-Bearer as forming 
an exception. The drawing has been made from 
actual measures of the bearing and distance, with- 
out any other supposition than that of an elliptic 
orbit with the greater component star in the focus. 

The other principal double star is, 
*, Its components are of the 4th and 6th magnitudes ; distant 
1" ; the greater yellow, the smaller bluish. From 1800 to 
1825, it did not appear double ; since 1825, it has been 



108 THE CONSTELLATIONS. 

separating more and more. The two stars revolve round 

each other in 88 years ; their mean distance is 1". 

In R. A. 25*2° 0', Dec. 3° 50', south, there is a round group 
of 10' diameter, containing a multitude of stars somewhat 
scattered. 

In R. A. 271° 0', Dec. 6° 49', there is a beautiful, bright, 
round nebula of 8' diameter. 

In R. A. 260°, Dec. 22°, south, there appeared, in October 
1604, a new star, of the 1st magnitude. It disappeared in 
September 1605. Kepler wrote an interesting work on this 
star. 

FABLE. 

Serpentaritjs vel Ophiuchtjs. — This constella- 
tion was originally iEsculapius, son of Apollo, god 
of Medicine, but killed by Jupiter with a thun- 
derbolt for his skill, particularly in having restored 
Hippoly tus to life. He is represented as grasping 
a serpent, the symbol of medicine, as well as of 
prudence and vigilance. 



Serpens — The Serpent. 

The head of the Serpent contains two stars, y 
and /3, of the 3d magnitude, with some smaller 
ones, and lies directly south of the Northern 
Crown, a, S and s are immediately below the 
stars just mentioned, and nearly in a line with £, 
in the knee of Ophiuchus ; and 5 and s near his 
left hand. The star p is due south of s about 10°. 
A line drawn from *j, in the right knee of Ophiu- 
chus, to 7, in the Eagle, will indicate the direction 
of the tail of the Serpent, which contains several 



THE CONSTELLATIONS. 109 

small stars, a is called Unuk ; <5, Jed ; &, Alya ; 
and X, Marsik. 

The double stars are : 

P Its components are of the 3d and 9th magnitudes ; distant 
31"; bluish white. 

5 of the 3d and 4th magnitudes ; distant 3" ; the former yel- 
lowish white, the latter ash-coloured. 

both of the 4th magnitude ; distant 22" ; yellowish white ; 
easily seen in small telescopes. 
In R. A. 218° 4', Dec. 15° 3', is a variable star, which, 

from being of the 8th magnitude, becomes invisible in the 

period of 353 days, and again increases to the 8th. 

In R. A. 235° 22', Dec. 15° 45', lies a variable star, which, 

from the 5th magnitude, becomes invisible in the period of 

340 days, and again increases to the 5th. 



Delphinus — The Dolphin. 

This beautiful little constellation, which lies 
between the Eagle, Antinous and Equiileus, may- 
be easily recognised by four stars, a, /3, y and <5, 
all of the 3d magnitude, which form a rhombus. 
Of these stars a is called Svalozin, and /3 Rotanew. 
A little to the south and west of the rhombus is 
another star, s, of the 3d magnitude. This is in 
the tail, the other four being in the head of the 
Dolphin. 

In this constellation we may notice among the double stars, 
/3 whose components are of the 3d and 11th magnitudes, both 

green, distant 33". 
y of the 4th and 5th magnitudes, distant 12". The greater 

is of a deep golden yellow colour, the smaller bluish green. 



110 THE CONSTELLATIONS. 

FABLE. 

The Dolphin is said to have been placed among 
the constellations for the assistance it afforded 
Neptune in procuring Amphitrite for his wife. 

Painters and sculptors represent the dolphin as 
a crooked hump-backed fish ; but, in reality, it is 
quite straight. 



Equuleus — The Little Horse. 

This little constellation lies between Pegasus, 
the Dolphin, and the Water-bearer. It may be 
known by four stars of the 4th and 5th magni- 
tudes, which form an elongated, irregular trape- 
zium, a is called Kitalphar. 
|3 is a fine double star, whose components are of the 4th and 

12th magnitudes. Sir John Herschel recommends this 

star as a good object for testing the quality of the best 

telescopes. 
s is a triple star, of the 6th, 6th, and 7th magnitudes, whose 

distances are J" and 11". 

FABLE. 

Equuleus. — This asterism is said to represent 
the horse which Mercury presented to Castor, and 
which he named Ceteris. 



Scutum Sobieski — Sobieski's Shield. 
Sobieski's Shield is one of the constellations 
instituted by Hevelius, between Antinous and the 
Serpent's tail, in the Milky-way. It may be 



THE CONSTELLATIONS. Ill 

found by a small triangle, formed by three small 
stars, which is intersected by a line drawn from 
x, in the knee of Antinous to £, in the left knee 
of Ophiuchus. At a little distance from this tri- 
angle, towards the Eagle, are several small stars. 

The star 1 varies from the 5th to the 6th magnitude, in a 
period of 60 days. 

In R. A. 280° 45', Dec. 6° 20', south, is a large, round, 
beautiful group of stars, which, with ordinary telescopes, 
appears as a bright nebula. Diameter 12'. 



Turdus Solitarius — The Solitary Thrush. 

This is north of Libra; was established by Le 
Monnier. This constellation contains only smaller 
stars. 



Vulpecula et Anser — The Fox and Goose. 

This constellation is situated south of the Swan, 
and north of the Dolphin and the Eagle ; was 
established by Hevelius. It contains many small 
stars, among which may be noticed : 
I In R. A. 295° 15', Dec. 18° 43', a double star ; its compo- 
nents are of the 6th and 9 th magnitudes ; distant 8" ; the 
greater greenish white, and the smaller blue. 
A triple star, 6th, 8th and 7th magnitudes; distances 11" 
and 71" ; colours respectively, yellowish white, ash-colour 
and yellow. 

In R. A. 294° 40', Dec. 26° 40', on the ear of the Fox, 
Anthelm saw, in June, 1670, a star of the 3d magnitude, 



112 THE CONSTELLATIONS. 

which had diminished to the 5th, in August, and in October 
of the same year, had entirely disappeared. In March, 1671, 
he saw i again, of the 4th magnitude ; and in March of the 
following year (1672), it appeared of the 6th magnitude. 
Since that time it has not been seen. 

In R. A. 300° 15', Dec. 20° 37', a large group of many 
stars, of the 10th to the 13th magnitudes, the largest of 
which is a double star. 

In R. A. 290° 45', Dec. 19° 55' a group of stars in the form 
of a trapezium, 3' long and 2' wide, and very close. 

In R. A. 303° 45', Dec. 19° 34', a planetary nebula, beau- 
tiful, round and bright, and throughout of the same degree 
of brightness. It is 2" in diameter, and around it stand four 
small stars, like so many satellites. 

In R. A. 312° 30', Dec. 29° 34', a nebula of 30' in length 
and 2' in breadth, some parts of which are densely studded 
with very small stars. 

In R. A. 298° 0', Dec. 22° 17', a very remarkable nebula. 



Sagitta — The Arrow. 
This is a small constellation under the Fox. 

FABLE. 

Sagitta. — According to the Greeks this was 
one of the arrows with which Hercules slew the 
vulture that gnawed the liver of Prometheus, 
when chained, by Jupiter's order, on the top of 
Mount Caucasus. 



THE CONSTELLATIONS. 113 

PLATE X. 
CONSTELLATIONS. 

Sagittarius The Archer. 

Scorpio The Scorpion. 

Lupus The Wolf. 

Ara The Altar. 

Norma, vel Quadra Euclidis The Rule. 

Telescopium The Telescope. 

Corona Australis . . . The Southern Crown. 



Sagittarius — The Archer, 

Contains the following stars : 

a Alrami. 6 The Middle Kaus. 

/3 l The First Urkab. s The Southern Kaus. 

/3 2 The Second Urkab. X The Northern Kaus. 

y Hushuba. 

This constellation occupies a large space south 
of Antinous and Sobieski's Shield. The bow lies 
in the Milky-way, and is marked by four stars, jm, 
X, 8 and s, all of the 3d magnitude. The arrow 
is marked by two stars, <r and 8, of the third mag- 
nitude, and three small stars in the head ; it points 
towards the Scorpion. The remainder of the 
constellation is composed entirely of small stars. 

Within this constellation there appear : 

In R. A. 276° 30', Dec. 24°, south, a beautiful, round group 
of stars, of which the brightness rapidly increases towards the 
centre. The stars of the 9th and 10th magnitudes are dis- 
persed throughout, but the edge is not well defined. 



114 THE CONSTELLATIONS. 

In R. A. 293° 30', Dec. 14° 33', south, a planetary nebula, 
with an obscure round disc of 10" diameter, with uniform light. 

In R. A. 268° 0', Dec. 23° 1', south, a forked nebula with 
three branches, a double star in the middle, and near this star 
a dark opening. 

FABLE. 

Sagittarius. — Chiron, the son of Saturn by 
Philyra, was a Centaur, or twofold being — half 
man and half horse. He was famed for his skill 
in medicine, music and archery, and instructed in 
the polite arts, the greatest heroes of his times. 
Being accidentally wounded with a poisoned arrow 
by Hercules, and the w 7 ound, which was incura- 
ble, causing him great anguish, Chiron prayed 
Jupiter to deprive him of immortality, that he 
might, by dying, be relieved from his excruciating 
pains. Jupiter assented to his request, and 
changed him into the constellation Sagittarius. 
The character of this sign (j) is an arrow; and 
the figure, a Centaur, in the act of discharging an 
arrow from a bow : both are supposed to denote 
the hunting season. The sun enters Sagittarius 
about the 22d of November. 



Scorpio — The Scorpion, 
Contains the following principal stars: 
a Antares. g Graffias. 

fi Akrab. X Schaula. 

S Dschubba. v Lesalh. 

The position of this constellation is easily de- 
termined by means of the bright star Antares, 



THE CONSTELLATIONS. 115 

which is due south of Ras Algethi in the foot of 
Hercules. West of Antares are /3, 6 and 7t, which 
form a curve ; and a little to the east of it is *. 
The tail is formed of several stars in a curved line 
concave upward ; the three stars, x, X and v, in 
the extremity of the tail, forming a small triangle. 

Among the doable stars are, 
6 of the 2d and 7th magnitudes ; distant 14/'; white and blue. 
a near a; of the 5th and 9th magnitudes; distant 21". 

FABLE. 

Scorpio. — Orion, a celebrated giant, having 
impiously boasted that there was not on earth an 
animal which he could not subdue, Diana, whom 
he had offended, sent a scorpion, which gave him 
a mortal sting, and was afterwards metamorphosed 
into this constellation. The character (m) is some- 
what like the letter m, with the last stroke pro- 
longed, and armed with a sting, or dart. It is 
supposed to be emblematic of the fevers and other 
diseases which prevail in autumn. In the ancient 
zodiacs this sign is represented by a snake, a cro- 
codile, Typhon, with scorpions' tails, instead of 
legs, and a sting in either hand ; or with serpents' 
tails for legs, his body bound round with a snake, 
and a staff in each hand. The sun enters the 
Scorpion about the 23d of October. 



Lupus— The Wolf, 
Lies to the south, under the Scorpion. This 
constellation is composed entirely of small stars. 



116 THE CONSTELLATIONS. 

Only the stars in the upper part of the Wolf rise 
above the horizon of Philadelphia. 



Ara — The Altar, 

Consists of small stars only. It is situated 
under the Scorpion's tail, and is not visible in the 
latitude of Philadelphia. 



Norma, vel Quadra Euclidis — The Rule and 
Square. 
The Rule and Square is between the tail of the 
Scorpion and the Wolf. This constellation was 
instituted by Lacaille, and only the northern part 
of it rises above our horizon. 



Telescopium — The Telescope, 

Between Sagittarius and the Scorpion, was like- 
wise introduced by Lacaille.* It is composed only 
of small stars, of which the northern ones alone 
are ever above our horizon. 



Corona Australis — The Southern Crown, 

Between Sagittarius and the Telescope, is com- 
posed of small stars, the largest being of the 5th 
magnitude. 



THE CONSTELLATIONS. 117 

PLATE XI. 
CONSTELLATIONS. 

Aquarius . . . . . The Water-bearer. 

Capricornus .... The Goat 

Piscis Australis . . . The Southern Fish. 

Globus iErostaticus . The Balloon. 

Microscopium . . . The Microscope. 

Grus The Crane. 

Phoenix . . . . . The .Arabian Bird. 

Apparatus Sculptoris . The Sculptor's Tools. 

Indus The Indian. 



Aquarius — The Water-bearer. 
The principal stars in this constellation are: 
a Sadalmelik. S Scheat. 

/3 Sadalsude. 6 Ancha. 

y Sadachbia. x Situla. 

a and (3 in the shoulders form with s in the nose 
of Pegasus and aof Equuleus, a quadrilateral figure, 
nearly rectangular. 5° to the east of a is 7 in the 
right arm ; and east of 7 are three small stars, two 
of which, 73 and x, with 7, form a right-angled tri- 
angle. These last are in the Urn, from which 
there issues a stream of water, which contains a 
number of small stars. <5 in the right leg forms 
with /3 and 7 an isosceles triangle, whose vertex is 
at 7. 

Of the double stars, we remark : 
§ in the right hand, both of whose components are of the 4th 
magnitude ; distant 3" ; colour greenish white. 



118 THE CONSTELLATIONS. 

In R. A. 339° 45', Dec 5° 8', south, a triple star, of the 
7th, 8th and 9th magnitudes ; distances 4" and 56". 

In R. A. 347° 30', Dec. 14° 24', south, a double star, of the 
5th and 7th magnitudes; distance, 13"; light yellow, and 
blue. 

In R. A. 353° 32', Dec. 16° 23', south, a changeable star, 
which, in a period of 382 days, fades from the 6th magnitude, 
until it entirely disappears, and again increases to the 6th. 

In R. A. 321° 15', Dec. 1° 34', south, a large, round, beau- 
tiful group of stars, easily resolvable, very bright toward the 
middle. The brightest part is 6" in diameter. 

In R. A. 313° 45', Dec. 12° 2', south, a planetary nebula, 
with a round disc, equally light throughout, and of 5' dia- 
meter. 

FABLE. 

Aquarius is supposed to be the same with 
Ganymedes, son of Tros, the builder of Troy, 
whom Jupiter translated to heaven to be his cup- 
bearer; or, according to other accounts, he is the 
representative of Deucalion, in whose time the 
Thessalian deluge happened. The character of 
this sign (jz) is a natural representative of gentle 
waves; and the figure, that of a man pouring out 
water from an urn, indicative of the moisture 
which prevails while the sun is passing through it. 
In the Egyptian zodiac, Canopus, with his pitcher, 
or cubit of justice, appears as the prototype of 
Aquarius with his urn. In the circular zodiac of 
Dendera, Aquarius is walking with a cup in each 
hand, while he balances upon a line or fine chain. 
At Esne, he appears in the same attitude, but 
with only one cup in his left hand, from which a 



THE CONSTELLATIONS. 119 

line or chain is hanging down. In the Egyptian 
zodiac, constructed by the second Hermes, Cano- 
pus, or Aquarius, is represented under the symbol 
of the Dea Multimamia ; and from the numerous 
paps on the body, an abundance of milk appears 
to flow, in allusion to the benefits derived from the 
overflowing of the Nile. In the Oriental zodiac, 
he sustains a vase, or cup of libation, in his right 
hand, and is habited in princely robes. The 
Etruscans represented the sun in Aquarius by 
Janus seated on a throne composed of twelve 
altars. The Egyptians call this sign Mon, or 
Meon, which is a solar title of very remote anti- 
quity, and indicative of a season of great mois- 
ture. The sun enters Aquarius about the 20th of 
January. 



Capricornus — The Goat 
The principal stars in this constellation are : 
a 1 first Dschabe. v JVashirah. 

a 2 second Dschabe. 6 Scheddi. 

(3 Dschabih. 
This constellation lies south of the Dolphin and 
Antinous, and west of Aquarius. S in the tail 
forms with 8 and y of Aquarius, an isosceles tri- 
an'gle, of which y is at the vertex. About 20° 
west of S is j8 in the head ; and a little above /3 
are a, v and f in the horns. Below f3 are the stars 
if and p in the head; and still lower in the same 
direction, are 4* an d w i n the leg. 



120 THE CONSTELLATIONS. 

In R. A. 302° 45', Dec. 15° 19', south, a very fine double 
star, a difficult object to detect; of the 17th and 18th (Her- 
schel's) magnitudes; distance 3"; near j3 Capricorni. Sir 
John Herschel selects this as a test object for the best tele- 
scopes. 

FABLE. 

Capricornus. — Pan, or Bacchus, fleeing from 
the giant Typhaeus into the river Nile, transformed 
himself into a sea-goat, and Jupiter made him a 
constellation. Or, Amalthoea, daughter of Melis- 
sus, king of Crete, nourished the infant Jupiter 
with goats' milk and honey ; for which service she 
was translated to the heavens, in the constellation 
Capricornus. The character of this sign (YS) is 
supposed to have some resemblance to the tail of 
a goat ; but it is more probably an ancient mark 
for the name. The figure is sometimes that of a 
monster, partly a goat and partly a fish ; but 
sometimes like a common goat, an animal fond of 
mounting, and therefore emblematical of the sun, 
which, having in this sign reached his greatest 
southern declination, begins to reascend toward 
the north. In the Egyptian zodiac, the sea-goat 
is held in a string by Anubis. In the Indian 
zodiac, this sign is represented by a goat passant, 
traversed by ajish; on the Oriental zodiac of Sir 
W. Jones, it is a fish swallowing an antelope, and 
surrounded by aquatic birds ; and in Moor's Hin- 
doo Pantheon, Capricornus is represented by an 
antelope. The sun enters Capricornus about the 
21st of December. 



THE CONSTELLATIONS. 121 

Piscis Australis — The Southern Fish. 
This constellation is situated under Aquarius. 
It is readily distinguished by means of a, or 
Fomalhaut, a star of the 1st magnitude, which, 
with the two stars (3 and s, forms a nearly equila- 
teral triangle. These three are the only important 
stars in this constellation. 



Globus ^Erostaticus — The Balloon. 
This constellation is situated under Capricor- 
nus, and west of the Southern Fish. It was intro- 
duced by Lalande. 



Microscopium — The Microscope, 
Is situated between Sagittarius and the Balloon. 
It was instituted by Lacaille. 



Grus — The Crane, 
Is south of the Southern Fish. It contains one 
star of the second magnitude, two of the third, and 
two of the fourth. 



Phcenix — The Phcenix, or Arabian Bird, 
Is situated east of the Crane. 

Apparatus Sculptoris — The Sculptor's Tools, 
Lies between the Phcenix and the Whale. 



122 THE CONSTELLATIONS. 

Indus — The Indian, 
Is under the Microscope, and westward from 
the Crane. 



The six last named constellations all lie very- 
far south ; only their northern parts rise to our 
view at Philadelphia. 



PLATE XII. 
CONSTELLATIONS. 

Cetus The Whale. 

Eridanus .... The River Po. 

Lepus The Hare. 

Harpa Georgii . . George's Harp. 

y i • " > . Sceptre of Brandenburgh. 
denburgium ) 

Apparatus Chemicus Chemical Apparatus. 

Machina Electrica . Electrical Machine. 

Caelum Sculptoris . The Graver. 

Horologium . . . The Clock. 



Cetus — The Whale. 
The principal stars are: 

a Menkar. 

(3 Diphda or Deneb Kaitos. 

o Mira. 

£ Batan Kaitos. 
This is one of the largest constellations in the 



THE CONSTELLATIONS. 123 

heavens. It lies chiefly under Aries and Pisces. 
The head and neck of this sea-monster may be 
known by the three stars, a, 6 and o, lying in a 
right line, 6 being midway between the other two. 
a forms an equilateral triangle with the Pleiades 
and a of Aries. A little above S is 7, and a line 
drawn from 7 through will show us 6 and v\ a 
little above the line, and £, (3 and r, a little below 
it. A line drawn from the Pleiades through a, 
will point out four stars, s, <x, g and tf, of the 4th 
magnitude, forming a parallelogram. 

Among the double stars are : 
7 Its components are of the 3d and 7th magnitudes ; distant 
2". 6 ; yellow and ash-coloured. Their proper motion among 
the other stars is 21" in a century'. 
v 5th and 10th magnitudes; distant 8"; yellow and ash- 
coloured. 
X 5th and 7th magnitudes ; distant 4" ; white, and yellowish 

white. 
4 is remarkable for its extraordinary proper motion of 181" 

in R. A. and 92" in Dec. in a century. 
o called Mira, or the wonderful, on the neck of the Whale ; 
a remarkable double star, of which the smaller can only 
be seen with the best telescopes, at a distance of 113" from 
the greater. The greater is variable, changing from the 2d 
magnitude to invisibility, and again to the 6th, in the period 
of 332 days. 

In R. A. 359° 0', Dec. 21° 40', south, is situated a group 
of stars in the form of a triangle. 

FABLE. 

Cetus. — The name of this extensive constella- 
tion, which occupies a greater space than any in 
the firmament, is derived, according to poetical 



124 THE CONSTELLATIONS. 

fiction, from the sea-monster which went to de- 
vour Andromeda. It was struck dead on behold- 
ing the head of Medusa, which Perseus presented 
to it, and was afterwards placed among the stars. 



Eridanus — The River Po. 

Eridanus, under Cetus and Taurus, and west 
of Orion. 

a Achernar. £ Zibah 

(3 Cursa. *\ Azha. 

7 Zaurak. o Beid. 

6 Rana. u Themin. 

This constellation may be traced from Rigel in 
the foot of Orion, under the Harp to the Whale; 
and thence, S. E. and S. W. in a serpentine direc- 
tion till it. sinks below the horizon. The princi- 
pal stars visible in our latitude are, 7, midway 
between Rigel and the parallelogram in the 
Whale; v\, near this parallelogram, in a line with 
7 and of the Whale; <$, about 5° N. W. of 7; 
s, making an equilateral triangle with v\ and <$; 
and u, in a line with in the neck of the Whale, 
and s of the River. 

The double stars are as follows : 

In R. A. 56° 15', Dec. 3° 27', south. Its components are 
of the 4th and 6th magnitudes ; distant 7". The greater is 
yellow, and the smaller blue. 

In R. A. 61° 56', Dec. 7° 54', south ; a double star of the 
5th and 8th magnitudes; distant 80". This double star 
has, next to 61 Cygni and p Cassiopceia, the greatest proper 



THE CONSTELLATIONS. 125 

motion. It amounts in a century to 219" in R. A. and to 
345" in Dec, whilst the distance of the two stars from each 
other hardly changes. 

FABLE. 

Eridanus, an ancient and celebrated river of 
Italy (now the Po), was made a constellation, 
because it received Phaeton when stricken of thun- 
der by Jupiter, after he had set the world on fire 
by his inexperience and temerity in presuming 
to drive the chariot of the Sun, his father. 



Lepus — The Hare. 

This is a small constellation, lying immediately 
under Orion. It may be known by the four prin- 
cipal stars, a or Arneb, /3 or JVikal, y and 5, form- 
ing a trapezium. About 4° south of Rigel are 
four small stars in the ears of the Hare, s forms 
with a and Rigel a triangle, right-angled at a. 

t On the left ear, in R. A. 76° 0', Dec. 12° 5', south, is a 
double star. Its components are of the 4th and 10th mag- 
nitudes; distant 13"; the greater greenish, and the smaller 
yellow. 

* on the same ear, in R. A. 76° 15', Dec.l3°9', south, is a 
double star of the 5th and 8th magnitudes ; distant 3" ; the 
greater is yellow, and the smaller blue. 



Harpa Georgii — George' s Harp. 

The Harp, between Taurus and Eridanus, east- 
wardly from the head of the Whale, was estab- 



126 THE CONSTELLATIONS. 

lished by Hell in the year 1791, in honour of 
George III. of England. 



Sceptrum Brandenburgium — The Sceptre of 
Brandenburgh. 

The Sceptre, or the Brandenburgh Sceptre, is 
situated between the Hare and the Harp. It 
consists of three small stars in a vertical line 
between Rigel and the parallelogram in the 
Whale, about one-fourth the distance from Ri- 
gel. It was formed in 1688 by Kirch, a Prus- 
sian astronomer. 



Apparatus Chemicus — The Chemical Apparatus, 

Is in the southern curve of Eridanus, and was 
instituted by Lacaille. 



Machina Electrica — The Electrical Machine, 

Under the Whale, and west of the Chemical 
Apparatus, was instituted by Bode. 



Caela Sculptoris — The Graver, 

Is south of the Sceptre, and west of the Hare. 
It was formed bv Lacaille. 



THE CONSTELLATIONS. 



127 



Horologium — The Clock, 

Between the Graver and Phoenix, was formed 
by Lacaille. 

The last six constellations are composed, for the 
most part, of very small stars. 



PLATE XIII. 

CONSTELLATIONS. 



Canis Major . . 
Argo Navis . . 
Columba . . . 
Felis .... 
Equiileus Pictoris 
Officina Typographica 
Pyxis Nautica . . 



The Great Dog. 

The Ship Argo. 

The Dove. 

The Cat. 

The Painter's Easel. 

The Printing Press. 

The Mariner's Compass. 



Canis Major — The Great Dog. 
The principal stars are : 

a Sirius. s Udara. 

(3 Mirza. £ Furud. 

y Muliphein. v\ Mudra. 

$ Wezen. 
This constellation lies to the S. E. of Orion. 
Sirius is the brightest of all the fixed stars. It is 



128 THE CONSTELLATIONS. 

in the head of the Dog, nearly in a line with the 
three stars in the belt of Orion. 7 in the head, 
and /3 in the left fore-paw, are nearly in a line 
with Sirius. About 15° S. E. of Sirius are three 
stars of the 2d magnitude, 8, s and v\, forming a 
triangle right-angled at 8; and between 8 and s, is 
a of the 3d magnitude. £, in the left hinder-paw T , 
forms w 7 ith /3, a and s, a trapezium, which is very 
nearly a rectangle. Besides the above, there are 
several stars of the 4th magnitude, and many 
smaller ones which may be easily found. 

Among the double stars are : 
fju in R. A. 102° 0', Dec. 13° 50', south. Its components are 

of the 5th and 8th magnitudes ; 3" apart; yellow and blue. 
v in R. A. 97° 15', Dec. 18° 31', south, of the 6th and 8th 

magnitudes; 17" apart; the greater reddish, the smaller 

blue. 

FABLE. 

Canis Major, according to the Greeks, w T as 
one of Orion's hounds; but the Egyptians, who 
judged of the rising of the Nile by the rising of 
this constellation, or rather of the great star Siri- 
us, which is comprised in it, represented it by the 
figure of a dog, the symbol of a watchful and faith- 
ful monitor. It was the representative of their 
deity Anubis, and had the same relation to the 
Nile that Cerberus had to the sun. 



THE CONSTELLATIONS. 129 

Argo Navis — The Ship Argo. 
The principal stars in this constellation are: 

a Can opus. 
? JVaos. 
x Markeb. 

Of this extensive constellation, only the north- 
ern part rises above our horizon. The star Cano- 
pus, of the first magnitude, on the end of the rud- 
der, is in brilliancy nearly equal to Sirius, but it 
does not rise to our view. 

The prow of the ship may be known by three 
stars of the 3d magnitude, i, x and at, S. E. of the 
stars in the lower part of the Great Dog, which 
with several smaller stars form a curve convex 
towards the Dog. A line drawn from 7 in the 
head, through r\ in the tail of the Great Dog, 
and produced as far below tj as 7 is above 
it, will terminate in £, a star of the 2d mag- 
nitude. 7° due south of £ is 7, also of the 2d 
magnitude. A line drawn from Sirius through *j 
in the tail of the Dog, will point out X, of the 2d 
magnitude. Due south of Sirius, and on a paral- 
lel line with X, is v. The other principal stars are 
too far south to be seen in our latitude. 

The double stars are : 

InR. A. 114° 22', Dec. 14° 16', south. Its components are 
of the 6th and 7th magnitudes; distant 16"; both white. 

In R. A. 115° 0', Dec. 11° 46, south, of the 5th and 7th 
magnitudes ; distant 3" ; the greater yellow, and the smaller 
blue. 



130 THE CONSTELLATIONS. 






FABLE. 

Argo Navis. — This constellation is believed by 
many to derive its name from the celebrated ship 
Argo, in which Jason and his companions went 
to Colchis, in quest of the golden fleece, and after- 
wards visited nearly all the known world. When 
the expedition was finished, Jason consecrated his 
ship to the god of the sea, and it afterwards be- 
came a constellation. Others suppose it was the 
ship in which Danaiis migrated from Egypt to 
Greece; and all agree that it was the first long 
vessel ever built. In truth, the ship Argo is no 
other than the Ark of Noah. 



Columba — The Dove* 
This lies southerly, under the Great Dog. It 
was introduced by Roger, in the year 1679. 



Felts— The Cat, 
Between Hydra and the Compass, was placed 
in the heavens by Lalande. 



Equuleus Pictoris — The Painter's Easel, 
Between the Ship, the Dove, and the Graver, 
was introduced by Lacaille. 



THE CONSTELLATIONS. 131 

Officina Typographic a — The Printing Press, 
Between the head of the Great Dog, the Uni- 
corn, and the Cat, was introduced by Bode. 



Pyxis Nautica — The Compass, 
Between the Cat and the northern part of Argo 

Navis, was established by Lacaille. 

The band slung around it denotes the line, or 

log-line, added by Bode. 



PLATE XIV. 
CONSTELLA TIONS. 

Hydra The Water-Serpent. 

Crater The Cup. 

Centaurus The Centaur. 

Corvus The Crow. 

Antlia Pneumatica . . The Air Pump. 

Robur Caroli .... Charles 9 Oak. 

Crux The Cross. 



Hydra — The Water-Serpent. 
The Water-Serpent is a very large constellation, 
extending under the Crab, the Lion, and the Vir- 
gin. The head may be known by four small stars 
situated south of the Crab, 6, s, £ and ri; the first 
of these is of the 3d, and the others are of the 4th 
magnitude. The star a, called Alphard, or Cor 



132 THE CONSTELLATIONS. 

HydrcB, is about 20° S. E. of the head ; there is no 
other bright star near it for which it can be mis- 
taken : a line drawn from y of the Lion, through 
Regulus, will show us this star, about 20° S. W. 
of Regulus. The three small stars, t, i and 6, north 
of Alphard, mark the first coil. From a, it winds 
by a serpentine course under the Sextant, the Cup 
and the Raven, and is marked by a number of 
small stars, which may easily be found by the aid 
of the map, when the positions of these other con- 
stellations are known. South of Spica, may be 
found the two stars y and sr, in the tail, which 
form, with Spica, a triangle, right-angled at 7. 
Among the double stars are : 

e of the 4th and 8th magnitudes; distance 3"; yellow and 
blue. 

In R. A. 126° 30', Dec. 7° 14'; of the 6th and 7th magni- 
tudes; distant 10"; yellowish and reddish yellow. 

u Hydrae in R. A. 199° 42', Dec. 22° 15', south, is a variable 
star, which changes from the 5th magnitude to invisibility 
in a period of 494 days. 

FABLE. 

Hydra. — This constellation is said to represent 
the Lernsean hydra, the destruction of which con- 
stituted one of the twelve labours of Hercules. 
Or, more probably, it was emblematic of the Nile 
at the period of inundation, if not of the poetic 
deluge. 



THE CONSTELLATIONS. 133 

Crater — The Cup. 

The Cup lies under the Great Lion, and between 
this constellation and the middle of Hydra. A line 
drawn from Arcturus, through S of the Virgin, 
will pass through it. The three principal stars, 
a, or Alkes, ft and 5, form an isosceles triangle, 
whose vertex is at a. y and £ are in a line with 
a, and y and 6 are in a line with ft. 

In R. A. 178° 15', Dec. 17° 55', are two nebulae 
running into each other. Both are much brighter 
toward the middle than near the edge. 

FABLE. 

Crater. — This cup, or goblet, w 7 as attributed 
to Bacchus by the mythologists, and seems an 
allegorised symbol of Noah's discovery of the art 
of making wine. The fabulists farther pretend 
that Apollo, intending to* sacrifice to Jupiter, sent 
a crow with a cup to fetch water; but the bird, 
being of a vagrant disposition, wasted his time in 
idle amusements, and at last, returning without 
the water, told Apollo that the stream was guard- 
ed by a venomous serpent. This falsehood was 
easily detected ; and Apollo, to punish the bird, 
placed him opposite to the cup, and charged the 
serpent never to allow him to drink. 



Centaurus — The Centaur. 
The Centaur lies between the tail of Hydra and 
the northern part of Argo Navis, and south of the 
10 



134 THE CONSTELLATIONS. 

Virgin. Only the northern part of this constella- 
tion rises to our view. Directly south of Spica, 
several small stars in the head, and i and & in the 
shoulders, may be seen. 

FABLE. 

Centaurus. — The Centauri were a people of 
Thessaly,who,as the mythologists pretended, were 
the progeny of Ixion and Nephele, or a cloud ; and 
they were represented as monsters, half men and 
half horses. A celebrated warfare was main- 
tained between them and their neighbours, the 
Lapithae, which ended in the overthrow of the 
Centauri. 



Corvus — The Crow, or Raven. 

The Crow, east of the Goblet, and south of the 
Virgin, may be easily recognised by four stars, of 
the third and fourth magnitudes, which form a 
quadrangle. A line drawn through s and 8 of the 
Virgin, would pass through 8 and near s and a of 
the Crow. 8 and /3 of the Crow are in a line 
with r\ Virginis, and j3 and y are nearly in a line 
with /3 of the Virgin. 

FABLE. 

Corvus. — This constellation is said to have been 
the Crow into which Apollo metamorphosed him- 
self when fleeing from the giant Typhaeus ; and 



THE CONSTELLATIONS. 135 

which was afterwards punished for insincerity, as 
is stated in the fable of the Crater. 



Antlia Pneumatica — The Air-Pump. 

The Air-Pump is between Hydra, the Goblet, 
and Argo Navis, and was introduced by Lacaille. 



Robur Caroli — Charles's Oak. 

Charles's Oak, between the Centaur and the 
northern part of Argo Navis, was placed in the 
heavens by Halley, in memory of King Charles 
II.-, of England. 

In R. A. 159° 0', Dec. 58° 40', south, near the star n of the 
oak, stands a very remarkable nebula, which has the appear- 
ance of a leg of mutton. 



Crux — The Cross, 

With one star of the 1st, two of the 2d, and one 
of the 3d magnitude, was instituted by Roger in 
the year 1679. 

Charles's Oak and the Cross do not rise above 
our horizon. These and the constellations further 
south are never visible to us ; it will therefore be 
sufficient to give their names and places here. 
They will all be found on the map of the Southern 
Hemisphere. 



136 THE CONSTELLATIONS. 

Right Ascension. South Declination. 

i A 1 / A — — — — ■> 

Tdcan— The American Goose From 330° to 20° From 58° to 73° 

Octans Hadl2Ianus— Hadleifs Octant . " 170 " 360 " 75 " 90 

Hydros— The Male Water Serpent u 10 " 60 " 62 "82 

Retictjla Rhomboidalis— The Rhomboi- 

dalNet M 54 " 70 " 59 "67 

Dorado vel Xiphias— 77ie Sword Fish.. " 60 "110 " 50 "76 

Mons Mensiformis— Table Mountain .. " 55 " 140 " 75 " 85 

Piscis Volans — The Flying Fish " 105 "135 " 66 "68 

Chameleon— The Cameleon " 110 "180 " 68 "81 

Avis— The Bee " 182 "210 " 63 "76 

Apis vel Avis Indica — The Bird of 

Paradise " 180 "260 " 67 "83 

Circinos— The Compasses " 215 "234 " 54 "65 

Triangulum Australe — The Southern 

Triangle or Level " 220 "252 " 62 "69 

Pavo— The Peacock " 265 "316 " 57 "75 

Indus— The Indian " 300 "343 " 48 "74 

Among the objects near the South Pole, the 
following are remarkable: 

The two Black Clouds, called also Cap-Clouds, 
Magellan's Spots, and Coal-Bags. The great black 
cloud extends from R. A. 185° 15' to 196° 15', 
and in Dec. from 61° to 64° south, and it lies on 
the east side of the Southern Cross. The double 
small black cloud is in R. A. 160° 0', and Dec. 62° 
south, near Charles's Oak. Both these striking 
dark spots are in a very bright part of the Milky- 
way. 

The two Southern Clouds are bright extensive 
nebulae. The great Southern cloud extends from 
R. A. 76° 45' to 90° 0', and from Dec. 69° to 71° 
south, and lies nearly on the South Pole of the 
Ecliptic. The small Southern Cloud lies in R. A. 
27° 30', and Dec. 73° 10, south. 



CALENDAR OF THE STARS. 137 



SEC. 12. 

THE CALENDAR OF THE STARS, OR AN EASY METHOD OF 
FINDING THE STARS FOR EVERY SEASON OF THE YEAR. 

JANUARY. 

About the Middle of the Month, at Half-past Nine o'clock in 
the Evening, 

The constellation Orion (Plate VI.) is nearly 
on the meridian ; and below him are the Hare and 
Dove (Plates XII. and XIII). The principal stars 
of Orion form a large quadrilateral, of which the 
two principal are in the shoulders: the Eastern, 
or principal star, is called Betelguex, and the 
western one Bellatrix* To the southward of them 
are three conspicuous stars, at equal distances 
from each other, called the belt of Orion. To the 
southward of his belt is his sword ; formed by a 
row of stars less brilliant than the belt. At about 
the same distance to the southward of the belt 
as Betelguex is to the northward of it, is Rigel £ 
and at the same distance from Rigel that Betel- 
guex is from Bellatrix, is a star called Saiph, on 
the knee, which, with the three last mentioned, 
forms the quadrangle enclosing the belt and sword. 

At an equal distance from Betelguex and Bella- 
trix, are three small stars, which constitute the 
head of Orion. 

The Little Dog (Plate VI.) is about 45 degrees 
high in the S. E. 



138 CALENDAR OF THE STARS. 

Capella, the principal star in the Charioteer 
(Plate VI.), is near the zenith. 

Sirius, in the Great Dog (Plate XIIL), is in the 
S. S. E. It forms nearly an equilateral triangle 
with Procyon and Betelguex, being the southern 
point. 

Alphard, or Cor Hydrce, in the Water Serpent 
(Plate XIV.), is in the E. S. E. about 19 degrees 
high. 

Castor and Pollux, in the Twins (Plate VI.), are 
in the east. The altitude of the former is 63 de- 
grees, and of the latter 58. The foot of Pollux is 
about 60 degrees high, S. E. 

Regulus, or Cor Leonis, in the Lion (Plate VIII.), 
is nearly due E. about 22 degrees high. Denebola, 
in the tail, is nearly E. N. E. about 5 degrees high. 

A line drawn from Regulus to Procyon, will 
pass the stars in the head of the Water Serpent 
(Plate XIV.), which are nearly at equal distances 
from these two. 

Berenice's Hair (Plate VIII.) is about 5 de- 
grees high, N. E. by E. 

Cor Caroli (Plate III.) is in the N. E. about 10 
degrees high. It is situated in the neck of Chara. 

Char a and Jlsterion are in the constellation of 
the Hounds (Plate III). 

Cor Caroli forms a triangle with Benetnasch in 
the tail of the Great Bear, and the third on the 
tip of the tail. 

In N. E. by N. are seen the seven stars in 
Ursa Major (Plate IV). Dubhe is 37 degrees 



CALENDAR OF THE STARS. 139 

high ; Alioth, in the tail, 22 ; and Benetnasch, 12 
degrees high. 

The principal star in the Dragon (Plate III.) is 
about 20 degrees high, N. N. E. 

Between the Great Bear and the Lion, is the 
Little Lion (Plate IV). 

A line drawn from Regulus through the Little 
Lion to the first and second stars, called the Point- 
ers, in the Great Bear, will pass through the elev- 
enth and twelfth of that constellation, in his left 
hind-foot. 

A little W. of the meridian is the Bull (Plate 
VI). Aldebaran, the principal star, surrounded 
by the Hyades, is about 65 degrees high, and his 
horns are on the meridian. The Pleiades are 
about 66 degrees above the horizon, S. W. by S. 

Nearly in the S. S. W. the star y in the River 
Po (Plate XII.), is about 33 degrees high. 

Menkar, in the Whale (Plate XII.), is about 43 
degrees high, S. W. by S. 

The Ram (Plate V.) is seen S. W. by W. and 
W. S. W. a Arietis, called the Eastern Horn, is 
about 47 degrees high. 

Algol, in Medusa's Head (Plate IV.), is above 
the Ram, about 66 degrees high. 

If a line be drawn obliquely from this last star 
to the zenith, it will pass near three other stars at 
almost equal distances from each other: the high- 
est is Alamach, in the foot of Andromeda (Plate 
V.) ; the next is Mirach, in the girdle ; and the 



140 CALENDAR OF THE STARS. 

lowest represents Mpheratz, her head, and the 
principal star in the constellation. 

Below Andromeda's head, the constellation Pe- 
gasus (Plate V.) is remarkable by its three stars, 
which form a square with Alpheratz. Markab is 
about 8 degrees high; Jllgenib due W. 20 degrees 
high; and Scheat W. N. W. 15 degrees high. 

A line drawn from Pollux, in the Twins (Plate 
VI.), to Regulus, in the Lion (Plate VIII.), passes 
through the Crab (Plate VI.). 

In the N. W. by W. the W formed by the five 
principal stars in Cassiopeia (Plate IV.), is about 
45 degrees high. 

N. W. by N. Deneb, called also Arided, in the 
tail of the Swan (Plate III.), is about 7 degrees 
high. 

The two bright stars in the Dragon (Plate III.) 
are due N. just at the horizon. 

Cepheus (Plate III.) is seen between the Dra- 
gon and Cassiopeia. 

The guards in the Little Bear (Plate III.), are 
at a little distance from the meridian. 



FEBRUARY. 

The Middle of the Month, about Half-past Nine o'clock, 

Procyon, in the Little Dog (Plate VI.), is a 
little east of the meridian, about 55 degrees high ; 
and a little higher is the second star in the con- 
stellation. 



CALENDAR OF THE STARS. 141 

Castor and Pollux, in the Twins (Plate VI.), are 
about 25 degrees above Procyon. 

N. of Gemini is the Lynx (Plate IV.); and S. 
of the Little Dog is the Unicorn (Plate VI.). 

Alphard or Cor Hydrce (Plate XIV.), is nearly 
S. E., 34 degrees high. 

Cor Leonis, or Regulus, in the Lion (Plate 
VIII.), is about 44 degrees high, in the E. S. E. : 
the star y in the Lion is about 8 degrees N. E. of 
it; Denebola, in the tail, is in the E., about 28 
degrees high ; and 8 in this constellation is 10 de- 
grees above Denebola. 

Alphard, the Hydra's Heart, forms, with Cor 
Leonis and Procyon, a large triangle. 

The two small stars E. by N. are in the hind- 
foot of the Great Bear (Plate IV.), about 42 de- 
grees high : two others are in the upper hind-foot, 
about 14 degrees above the two former. 

Nearly N. E. are the seven stars in the Great 
Bear, known by the name of Charles's Wain : the 
lowest, called Benetnasch, is at the tip of the 
tail, about 25 degrees high ; Dubhe, the north- 
ernmost, and one of the pointers, is 50 degrees 
high. 

Cor Caroli (Plate III.) is 27 degrees above the 
horizon, N. E. by E. 

Berenice's Hair (Plate VIII.) is very conspi- 
cuous, between Denebola and Cor Caroli. 

Etanin, the second star of the Dragon (Plate 
III.), and the third, are N. by E. about 5 degrees 



142 CALENDAR OF THE STARS. 

high ; the first, or a, is about 30 degrees high, in 
the N. E. by N. 

The Virgin (Plate VIIL), is partly risen in 
theE. 

Betelguex, in the right shoulder of Orion (Plate 
VI.), about 54 degrees high; and Rigel, in his left 
foot, about 34 degrees high, are nearly in the S. 
W. Bellatrix, the star in the left shoulder, is about 
49 degrees high. The three stars in the middle 
are called his belt 

Sirius, in the Great Dog (Plate XIII.), about 33 
degrees high, a little W. of the meridian, forms, 
with Bellatrix and Procyon, a large triangle. 

The south horn of the Bull (Plate VI.) is about 
62 degrees high, S. W. by S. ; and the northern 
horn is 66 degrees high, W. S. W. Mdebaran r 
the eye, is 50 degrees high. The Pleiades are 
more to the W., 45 degrees high. 

Capella, or Mioth, in the Charioteer (Plate 
VI.), is W. N. W., about 68 degrees high ; and the 
second star, of the second magnitude, in the right 
shoulder, is 76 degrees high. 

Menkar, in the Whale (Plate XII.), is about 25 
degrees high, W. by S. 

a, in the northern horn of the Ram (Plate V.), is 
about 25 degrees high, W. by N. 

Medusa's Head (Plate IV.), is about 45 degrees 
high, nearly W.N. W. 

Mamach, in Andromeda (Plate V.), is about 34 
degrees high, N. W. by W. ; and below it is Mi" 
rach, 22 degrees high. 



CALENDAR OF THE STARS. 143 

The principal stars in Perseus (Plate IV.) are 
above Alamak. 

Cassiopeia (Plate IV.) is nearly N. W. by N. 

Cepheus (Plate III.) is N. by W. 

The body of the Little Bear (Plate III.) is be- 
tween the Dragon and the Pole-star. 



MARCH. 

Middle of the Month, about half-past Nine o'clock, 

Alphard, or Cor Hydrce, in the Water-Serpent 
(Plate XIV.), is near the meridian, about 42 de- 
grees high. 

Cor Leonis, or Regulus, in the Lion (Plate IV.), 
is a little to the E. of the meridian, about 60 de- 
grees highland above it are five others in the 
head and mane.. One on the back is about 58 de- 
grees high, E. S. E. ; and Denebola, in his tail, is a 
little more eastward, 48 degrees high. 

Spica, in the Virgin (Plate VIII.), is nearly S. 
E. by E, about 14 degrees high. Between Spica 
and Denebola, in the Lion, are five or six stars in 
the Virgin. Vindemiatrix, in this constellation, is 
more to the E., and about 33 degrees high. 

Arcturus, in Bootes (Plate VII.), is E. by N., 
about 24 degrees high. 

Spica, Denebola, and Arcturus, form a triangle 
almost equilateral. 

Regulus, or Cor Leonis, Cor Caroli, and Vinde- 



144 CALENDAR OF THE STARS. 

miatrix, in the Virgin, form a triangle, within 
which is Berenice's Hair (Plate VIII). 

Mirach, in Bootes, is about 23 degrees high, E. 
by N. E. ; and the two stars in his shoulder are a 
little more E. 

The Northern Crown (Plate VII.) is below 
these two stars; and Alphecca, the principal star 
in this constellation, is about 13 degrees high. 

Mkalurops, in the head of Bootes, is nearly N. 
E. by E., about 27 degrees high. 

Benetnasch, the lowest star in the tail of the 
Great Bear (Plate IV.), is about 42 degrees high, 
N. E. by E.; Mizar about 6 degrees higher, and 
Alioth about 4 degrees higher still. 

The Little Bear (Plate III.) is in a favourable 
position for observation; and between this con- 
stellation and the three stars above-mentioned, in 
the Great Bear, the principal star in the Dragon 
(Plate III.) may be seen in the N. E., 42 degrees 
high. More to the N. and about 30 degrees lower, 
may be seen Etanin and three other stars in the 
head of the Dragon. 

The Cup and the Crow, with the constellation 
of the Water-Serpent (Plate XIV.), occupy a 
large space from S. to S. E. by E. 

Below Bootes is seen a part of Hercules (Plate 
VII.). 

Sirius, in the Great Dog (Plate XIII.), about 25 
degrees high, is nearly in the S. W. On each side, 
and at nearly equal distances from it, are two 
stars, one in his foot, the other in the neck. 



CALENDAR OF THE STARS. 145 

The Little Dog (Plate VI.) is more to the S., 
about 26 degrees higher. 

Castor arid Pollux, in the Twins (Plate VI.), are 
about 70 degrees high, W. S. W. The foot of 
Pollux is about 50 degrees high. 

Orion (Plate VI.), occupies the space between 
W. by S., and S. W. by W. Rigel, in the heel, 
is about 9 degrees high ; and Betelguex, in the 
shoulder, is about 27 degrees high. 

Between Betelguex and Castor and Pollux are 
four stars, forming an imperfect square in the feet 
and knees of the Twins. 

Sirius and Betelguex form nearly an equilateral 
triangle with Procyon, in the Little Dog. 

The Unicorn (Plate VI.) is between Sirius and 
Procyon. 

Aldeharan, in the Bull (Plate VI.), is due W., 
about 28 degrees high; and the south horn is 
about 41 degrees high: these two stars and Betel- 
guex form a triangle. The northern horn of the 
Bull is about 17 degrees above Aldebaran. 

Capella, or Mioth, in the Charioteer (Plate 
VI.), is about 48 degrees high, W. N. W. 

Algol, in Medusa's Head (Plate IV.) is about 24 
degrees high, N. W. by W. 

Perseus (Plate IV.) is a few degrees higher. 

Andromeda (Plate V.) and Cassiopeia (Plate 
IV.) are more to the north. 



146 CALENDAR OF THE STARS. 

APRIL. 

Middle of the Month, about half-past Nine o' ] clock. 

The Great Bear (Plate IV.) is on the meridian, 
a little N. of the zenith ; the lower star in the tail 
(one of those called Charles's Wain) is about 62 
degrees high. 

Below the hind foot of the Bear, the fourth star 
on the back of the Lion (Plate VIII.) is on the 
meridian, about 72 degrees high. 

Deneb, or Arided, in the Swan, (Plate III.) is 
about 2 degrees high, N. N. E. 

A line drawn from Deneb northwards to the 
Little Bear, will pass through the Dragon (Plate 

in.). 

Vega, in the Lyre (Plate VII.), is between N. 
E. and N. E. by E., about 10 degrees high. 

A line carried from Vega towards the body of 
Charles's Wain, will pass nearly by the two stars 
in the head of the Dragon ; and, 30 degrees higher, 
the principal star in that constellation is seen. 

Two stars in the E. by N., one about 5 degrees, 
the other about 10 degrees high, are Ras Alhague, 
in the head of the Serpent-Bearer (Plate IX.) ; 
and Ras Algethi, in the head of Hercules (Plate 
VII.). 

Alphecca, in the Northern Crown (Plate VII.), 
is E. by N., about 36 degrees high. 

E. by S., extending from the horizon to 30 de- 
grees high, is a part of the constellation Serpent 
(Plate IX.). 






CALENDAR OF THE STARS. 147 

Arcturus, in Bootes (Plate VII.), is about 46 
degrees high, E. by S. ; and about 26 degrees 
higher is Charles's Heart (Plate III,). 

The Scales (Plate IX.) is more to the S., about 
15 degrees above the horizon. 

Spica, in the Virgin (Plate VIII.), is in the S. 
E. by S., about 32 degrees high ; and, 23 degrees 
higher, is Vindemiatrix, in the arm of the same 
constellation. 

Berenice's Hair (Plate VIII.) is about 70 de- 
grees high, a little more to the E. 

The upper part of Centaurus (Plate XIV.) is 
just above the horizon, in the S. E. by S. 

Denebola, in the tail of the Lion (Plate VIII.), 
is between S. S. E. and S. by E., about 65 degrees 
high. Cor Leonis, or Regulus, is about 60 degrees 
high, S. S. W. 

A line carried from Denebola to the horizon 
will pass through the head of the Virgin, and 
through the Crow and the Water-Serpent. 

Cor HydrcB (Plate XIV.) is in the same azimuth, 
about 37 degrees high. 

The Little Dog (Plate VI.) is W. S. W.; and 
the Unicorn (Plate VI.) below him. 

Sirius is a little more to the S., 7 degrees high. 

Betelguex, in Orion (Plate VI.), is due W., about 
12 degrees high. 

Castor, in the Twins (Plate VI.), is about 47 
degrees high. 

Aldebaran, in the Bull (Plate VI.), is more to 
the N., about 4 degrees high. The northern horn 



148 CALENDAR OF THE STARS. 

of the Bull is between W. N. W. and W. by N., 
about 21 degrees high. 

Capella, or Alioth, in the Charioteer (Plate 
VI.), is N. W. by W., 27 degrees high ; and the 
second star in this constellation is about 34 de- 
grees high. 

Algenib, in Perseus (Plate IV.), is between N. 
W. by N. and N. W., about 13 degrees high. 

Algol, in Medusa's Head (Plate IV.), is about 
7 degrees high. 

Cassiopeia (Plate IV.) is in N. by W. 



MAY. 

Middle of the Month, about half-past Nine o'clock. 

Cor Caroli is in the zenith. 

Mizar, the middle star in the tail of the Great 
Bear (Plate IV.), is on the meridian, and 15 de- 
grees N. of the zenith. 

Spica and Vindemiatrix, in the Virgin (Plate 
VIII.), are near the meridian; the former 40, and 
the latter 62, degrees high. 

Cepheus (Plate III.) is in the N. N. E. Aide- 
ramin, the principal star in Cepheus, is about 22 
degrees high. A line drawn from Cepheus to- 
wards the zenith, will pass near the Little Bear 
(Plate III.). 

Deneb, or Arided, in the Swan (Plate III.), is in 
the N. E., about 13 degrees high. 

Vega, in the Lyre (Plate VII.), is about 30 de- 



CALENDAR OF THE STARS. 149 

grees high, E. N. E.; and Albiero, in the beak of 
the Swan, is about 15 degrees below it. 

The stars in the body of the Dragon (Plate III.), 

are between Cepheus, the Swan, the Lyre, and 

the Little Bear. The stars in the head of the 

Dragon are N. E. of Vega, and about 40 degrees 

igh. 

Ras Mhague, in the Serpent-Bearer (Plate 
X.), is due E., about 27 degrees high; and Ras 
ilgetM, in Hercules (Plate VII.), a little more to 
the S., about 32 degrees high. 

The Northern Crown (Plate VII.) is about 58 
degrees high, in E. by S. 

The Serpent (Plate IX.) is more to the S., and 
extends from 50 degrees to the horizon. 

The two stars in the shoulders of Bootes (Plate 
VII.) are nearly in a line, towards the zenith, with 
Gemma, in the Northern Crown. 

The Scales (Plate IX.) occupy the space from 
S. S. E. to S. E. 

Arcturus, in Bootes, is about 66 degrees high, 
S. E. nearly. 

Algenib, in Perseus (Plate IV.), is about 5 de- 
grees high, in N. N. W. 

Capella, in the Charioteer (Plate VI.), is 9 
degrees high, in N. W. by N. ; and the star in his 
shoulder 16 degrees high. 

Dubhe, in the Great Bear (Plate IV.), is a little 
more N., about 60 degrees high; and the whole 
of this constellation is now in a favourable position 
for observation. 
11 



150 CALENDAR OF THE STARS. 

Castor and Pollux, in the Twins (Plate VI.), are 
W. N. W., about 24 degrees high. 

Procyon, in the Little Dog (Plate VI.), is due 
W., about 9 degrees high. The Crab (Plate VI.) 
is above it. 

The Lion (Plate VIII.) occupies the space be- 
tween W. by S. and S. W. by S. Denebola, in 
the tail, is 60 degrees high; and Cor Leonis, or 
Regvlus, is about 42 degrees high. 

Cor Hydrce, or Mphard (Plate XIV.), is about 
23 degrees below Regulus, and about 20 above 
the horizon. The whole of the Hydra may now 
be seen, extending .from the stars in the head, in 
W. by S. to S. S. E. It occupies nearly a hori- 
zontal line, under the Lion and Virgin, of almost 
90 degrees. 

In the intermediate space, three more constella- 
tions are supported on the Hydra, viz. : the Sex- 
tant, under the Lion ; the Cup, under the Lion 
and Virgin; and the Crow, between the southern 
wing of the Virgin and the tail of the Hydra. 

Berenice's Hair (Plate VIII.) is seen between 
the Virgin and Cor Caroli. 



JUNE. 

Middle of the Month, about Ten o 'clock. 
The Little Bear (Plate III.) is on the meri- 
dian ; and Alruccaba, the Pole-star, may be easily 
discovered at the end of his tail, the body of the 
Bear being above the Pole. 



CALENDAR OF THE STARS. 151 

The Northern Crown (Plate VII.) is also on 
the meridian, about 80 degrees high, or 10 degrees 
south of the zenith ; and the head of the Serpent 
(Plate IX.) about 10 degrees lower. 

Half-way between the Pole-star and the N. N. 
E. point of the horizon is Cassiopeia (Plate IV.), 
the principal stars of which, five in number, ap- 
pear like an inverted chair. Schedir, the prin- 
cipal star, is about 13 degrees high. 

Alderamin, in Cepheus (Plate III.), is in the N. 
E. by N., about 37 degrees high ; and the three 
stars in his crown are 10 degrees lower. 

Scheat, in Pegasus (Plate V.), is about 6 degrees 
high. A line drawn from this star to the head of 
Cepheus, will pass through the Lizard (Plate III.). 

Deneb, or Arided, in the Swan (Plate III.), is 
about 36 degrees high, in N. E. by E. 

The stars in the head of the Dragon (Plate III.) 
are in the N. E., 65 degrees high. 

Nearly due E., about 22 degrees high, is the 
Dolphin (Plate IX.) ; 42 degrees high, is Albiero, 
in the beak of the Swan ; and, 57 degrees high, 
Vega, in the Lyre (Plate VII.). 

Atair, in the Eagle (Plate IX.), is 27 degrees 
high, E. by S. nearly. 

Antinous (Plate IX.) is more to the S. ; and the 
three stars in his foot are about 25 degrees high. 

Ras Algethi, in Hercules (Plate VII.), is about 
58 degrees high, and the whole of the constellation 
extends nearly to the zenith. 



152 CALENDAR OF THE STARS. 

Ras Alhague, in the Serpent-Bearer (Plate 
IX.), is 55 degrees high, and the constellation oc- 
cupies the space from S. E. to S. 

Antares, in the Scorpion (Plate X.), is 22 de- 
grees high, S. by E., below the foot of the Ser- 
pent-Bearer. Antares forms a large triangle, 
with Arcturus and Spica Virginis westward, and 
with Vega eastward. 

Poniatow'ski's Bull (Plate VII.) is between the 
Eagle and Serpent-Bearer; Cerberus (Plate VII.) 
is above Poniatowski's Bull ; and the Archer is 
near the horizon, below the Serpent-Bearer. 

Perseus (Plate IV.) is in the N., partly above 
the horizon; and between this constellation and 
the Pole-star is the Cameleopard (Plate IV.), 

Dubhe, in the Great Bear (Plate IV.) is 44 
degrees high, N. W. 

Cor Leortis, in the Lion (Plate VIIL), is nearly 
due W. 14 degrees high; the hind-foot of the 

© O 7 

Great Bear 32 degrees high ; and Benetnasch, in 
the tail of the Bear, 68 degrees high. 

Cor Caroli (Plate III.) is 60 degrees high, 
nearly W. by N. 

Denebola, in the tail of the Lion, is 36 degrees 
high. 

Berenice's Hair (Plate VIII.) is 50 degrees 
high, between W. by S. and W. 

The Virgin (Plate VIII.) occupies the space 
from W. S. W. to S. S. W. ; Vindemiatrix is about 
48 degrees high, in S. W. by W. ; and Spica be- 
tween S. W. and S. W. by S. 32 degrees high. 



CALENDAR OF THE STARS. 153 

Arcturus, in Bootes (Plate VII.), is in the S. W., 
and its altitude is §b degrees. Alkalurops, in his 
head, is nearly in the zenith. 

The chief star in the Scales (Plate IX.) is be- 
tween S. S. W. and S. by W. 25 degrees high. 

Below the Scales is the Owl ; and below that is 
the Wolf, in the meridian. N. W. of the Wolf 
is the head of the Centaur. 

The Cup, the Crow, and the tail of the Hydra 
(Plate XIV.), are under the Virgin. 



JULY. 

Middle of the Month, about Three-Quarters past Nine d'cloch. 

The head of the Dragon (Plate III.) is on the 
meridian, and 12 degrees N. of the zenith. 

A line drawn from Etanin to the N. E. on the 
horizon, will pass Alder amin, in Cepheus (Plate 
III.), 48 degrees high ; the three stars in his head, 
40 degrees high ; and by Mirach, the second star 
in Andromeda (Plate V.), about 16 degrees high. 

Cassiopeia (Plate IV.), whose stars form a W 9 
is N. E. by N. between 20 and 30 degrees high. 

Perseus (Plate V.) is in the N. N. E. ; Algenib, 
in his side, is about 4 degrees high. The third 
star y in Perseus is about 9 degrees high. 

Alamak, in the foot of Andromeda, is in the N. 
E. by N., the same altitude as Algenib, in Per- 
seus; and E. N. E. 12 degrees high, is Alpheratz, 
in the head of Andromeda. 



154 CALENDAR OF THE STARS. 

Algenib, in Perseus, Alamak, Mirach, and the 
star in the head of Andromeda, form a line nearly 
parallel with the horizon. 

Algenib, in the wing of Pegasus (Plate V.), is in 
the horizon E. by N. nearly ; Scheat, 23 ; and Mar- 
ked), E. by N. about 14 degrees high. 

These three stars and Alpheratz, in the head 
of Andromeda, form a large square. 

About 37 degrees high, nearly due E., is seen 
a star in the extremity of the southern wing of 
the Swan (Plate HI.) ; and at 54 degrees high, 
Deneb, or Arided. The extremity of the upper 
wing is about 66 degrees high. 

The Lizard (Plate III.) is between the Swan, 
Cepheus, Andromeda, and Pegasus. 

Enir, in the mouth of Pegasus (Plate V.), is E. 
by S. about 26 degrees high. 

The Dolphin (Plate IX.) is E. S. E. 40 degrees 
high. 

Altair, in the Eagle (Plate IX.), is S. E. and 
S. E. by S. about 45 degrees high. 

Albiero, in the beak of the Swajv (Plate III.), is 
62 degrees high, and Vega, in the Lyre (Plate 
VII.), is due E. about 77 degrees high. 

The Fox and Goose (Plate IX.) are between 
Albiero and Altair. 

The Archer (Plate X.), the Goat (Plate XL), 
and the Water-Bearer (Plate XL), occupy the 
space from S. to E. S. E. 

The two principal stars in the Goat are about 



CALENDAR OF THE STARS. 155 

22, and the two principal stars in the Water- 
Bearer about 15 degrees high. 

The Great Bear (Piate IV.) is in the N. W., 
and a line drawn through the upper Pointer to 
the zenith will pass through the star of Draco 
(Plate III.), which is midway between the two 
principal stars in the square of Ursa Minor, and 
the second in the tail of Ursa Major. 

Charles's Heart (Plate III.) is 41 degrees high, 
W. N. W. 

Denebola, in the Lion (Plate VIII.), is 15 de- 
grees high, W. by N. 

Berenice's Hair (Plate VIII.) is 30 degrees 
high, in the same azimuth. 

Vindemiatrix, in the Virgin (Plate VIII.), is 28 
degrees high, nearly due W. ; and Spica, W. S. W. 
16 degrees above the horizon. 

The southern shoulder of Bootes (Plate VII.) 
is due W. 65 degrees high; the northern nearly 
W. by N. 58 degrees high ; and Arcturus about 
47 degrees high. 

The Northern Crown (Plate VII.) is W. S. W. 
nearly 65 degrees high. 

The southern star in the Scales (Plate IX.) is 
25 degrees high, S. W. by S. nearly; and the 
northern star 34 degrees. 

Antares, or Cor Scoiyionis, in the Scorpion 
(Plate X.), is 23 degrees high, S. S. W. 

A line draw T n from Antares to the zenith will 
pass through the Serpent-Bearer (Plate IX.), 
a^'i Hercules (Plate VII.), which are a little W. 



156 CALENDAR OF THE STARS. 

of the meridian. Ras Mhague and Ras Algethi 
are on opposite sides of the meridian, 65 degrees 
high. 



AUGUST. 

Middle of the Month, about Ten o'clock. 

Capella, in the Charioteer (Plate VI.), is be- 
tween N. E. by N. and N. N. E. 3 degrees high. 

Perseus (Plate IV.) is in the N. E. Algol, in 
Medusa's Head, called the second in Perseus, is 
about 12 degrees high. 

Cassiopeia (Plate IV.) is above Perseus, about 
40 degrees high. 

Mamah, in the foot of Andromeda (Plate V.), is 
22 degrees high, N. E. by E. nearly. Mirach is 
27 degrees high in E. by N. ; and the first star in 
Andromeda, E. by N. about 35 degrees high. 

The two stars in the head of the Ram (Plate V.) 
are seen below Mirach, about 15 degrees high. 

The Triangles (Plate V.), and the Fly (Plate 
V.), are between the Ram and Andromeda. 

The three stars in Pegasus (Plate V.), which, 
with the one in the head of Andromeda, form a 
square, are in a favourable situation for observa- 
tion. Algenib, the third, is due E 2G degrees high ; 
Markab, the first, E. S. E. nearly, is 39 degrees 
high; and Scheat, the second, is due E. 48 degrees 
high. Enir, in the mouth of Pegasus, is about 49 
degrees high, S. E. 



CALENDAR OF THE STARS. 157 

A line drawn from S. E. by E. to the zenith, 
will pass some stars in the neck of Pegasus; and 
at 63 degrees will pass a star in the tip of the 
wing of the Swan (Plate III.) ; and Deneb, or Art- 
ded, the principal star in that constellation, is 77 
degrees high, the northern wing being in the 
zenith. 

Scheat, in the leg of the Water-Bearer (Plate 
XI.), is S. E. about 18 degrees high: about 38 
degrees high is the principal star in this constella- 
tion ; and 37 degrees high, is the second in his left 
shoulder. 

The Dolphin (Plate IX.) is 62 degrees high, S. 
S. E. 

The Fox (Plate IX.) is about 10 degrees higher. 

The two stars in the Goat (Plate XL) are S. 
by E. about 35 degrees high. 

Altair, in the Eagle (Plate IX.), is on the meri- 
dian, 59 degrees high; Mbiero, in the beak of 
Cygnus (Plate III.), 20 degrees higher. 

Gepheus (Plate III.) is in the N. E. above Cas- 
siopeia ; and between Pegasus, Andromeda, Cas- 
siopeia, Cepheus, and the Swan, the Lizard 
(Plate III.) is seen, E. N. E. 

The Archer (Plate X.) occupies a space be- 
tween S. and S. S. W. Some degrees higher are 
Sobieski's Shield and Poniatowski's Bull (Plate 
VIL). 

10 degrees above the horizon, Antares, in the 
Scorpion (Plate X.), is seen S. W. ; about 52 de- 
grees high, Ras Jllgethi, in Hercules (Plate VIII.), 



158 CALENDAR OF THE STARS. 

and Ras Alhague, in the Serpent-Bearer (Plate 
IX.) ; and about 30 degrees higher, near the ze- 
nith, is Vega, in the Lyre (Plate VII.). 

The second star of the Scales (Plate IX.) is W. 
S. W. 13 degrees high ; above which, more to the 
W., are some stars in the head of the Serpent 
(Plate IX.). 

The Northern Crown (Plate VII.) is nearly- 
due W. 

Arcturus, in Bootes (Plate VII.), is 20 degrees 
high, W. by N. ; 20 degrees higher, the star in the 
right shoulder of Bootes. A line drawn from the 
last star towards the zenith, will pass a little S. 
of the leg of Hercules (Plate VII.) and the stars 
in the head of the Dragon (Plate III.). 

Berenice's Hair (Plate VIII.) is N. W. by W., 
just above the horizon. 

Charles's Heart (Plate III.) is 18 degrees high, 
in the same azimuth, surrounded by the stars in 
the Hounds. 

Above Charles's Heart is Benetnasch, in the 
tip of the tail of the Great Bear (Plate IV.) ; and 
a little above it, are three stars, near the hand of 
Bootes (Plate VII.). 

The Great Bear is 20 degrees high, N. N. W., 
and Kochab, one of the guards in the Little Bear 
(Plate III.), is 44 degrees high ■ the Pole star is to 
the E. of it. 



CALENDAR OF THE STARS. 159 

SEPTEMBER. 
Middle of the Month, about Ten o'clock. 

The Lynx (Plate V.) occupies the space com- 
prehended between N. E. by N. to N. by E., with 
his head 17 degrees above the horizon. 

The Cameleopard (Plate IV.) is above the 
Lynx, extending from N. E. to the Pole. 

Capella, in the Charioteer (Plate VII.), is in 
the N. E., 14 degrees high; and his companion, 
the second in the Charioteer, is a few degrees 
lower, towards the N. 

The north horn of the Bull (Plate VI.) is in the 
N. E. by E., about 4 degrees high. About 30 
degrees higher is seen Algenib, in Perseus (Plate 
IV.) ; and Cassiopeia (Plate IV.) is still higher, 
and more to the N. 

Aldebaran, in the Bull, is rising, with the Hy- 
ades, E. N. E. ; the Pleiades are about 17 degrees 
high, more to the E. 

The foot of Perseus (Plate IV.) is to the N. E. 
of the Pleiades ; and Algol, in the Head of Medusa, 
about 10 degrees higher. 

Alamak, in Andromeda, (Plate V.), is E. N. E., 
43 degrees high; below which are the Triangles 
(Plate V.), the Fly, and the tail of the Ram (Plate 
V.). Arietis, the northern horn of the Ram, nearly 
due E., is about 33 degrees high. 

Mirach, in Andromeda, is 50 degrees high ; the 
star in the hand, towards the zenith, is 63 degrees 



160 CALENDAR OF THE STARS. 

high. The head of Andromeda is nearly E. by S., 
58 degrees high. 

Menkar, in the Whale (Plate XII.), is about 10 
degrees high, under Arietis. This constellation 
occupies a space from E. to S. E. by S., and nearly 
30 degrees from the horizon. 

Algenib, in Pegasus (Plate V.), is S. E. by E. ; 
Sc/teat, 70 degrees high; and Markab, 58 de- 
grees. 

The four last-mentioned stars form a conspicu- 
ous square. 

Fomalhaut, in the Southern Fish (Plate XL), is 
about 17 degrees high, S. by E. nearly. 

Scfieat, in the Water-Bearer (Plate XL), is 
more to the E. and higher. The greater part of 
this constellation is on or near the meridian. 

Enir, in the mouth of Pegasus (Plate V.), is on 
the meridian, 60 degrees high; and, about 20 de- 
grees higher, is the star in the southern wing of 
the Swan (Plate III.). 

The head of Cepheus (Plate III.) is 20 degrees 
N. of the zenith. 

Two stars in the head of the Goat (Plate XL) 
are 32 degrees high ; those in his tail are more to 
the S. 

The Dolphin (Plate IX.) is in the same azimuth, 
60 degrees high. 

Anti\ous (Plate IX.) is S. W. by S. The star 
in his knee is 35 degrees high. 

Altair, in the Eagle (Plate IX.), is 50 degrees 



CALENDAR OF THE STARS. 161 

high, in the same azimuth; and the two stars in 
the tail of the Eagle are in the same altitude, S. 
W. by W. 

Below the tail of the Eagle is the Bull of Po- 
niatowski (Plate VII.) ; above it is Alhiero, in the 
beak of the Swan (Plate III.); and almost in the 
zenith is Den eb, or Arided, in the same constella- 
tion. 

Ras AUiague, in the head of the Serpent-Bearer 
(Plate IX.), and Ras Algethi, in the head of Her- 
cules (Plate VII.), are W. by S., nearly 30 de- 
grees high. 

Vega, in the Lyre (Plate VII.), is a little more 
to the W., 57 degrees high ; above w 7 hich is the 
northern wing of the Swan (Plate III.). 

The head of the Serpent (Plate IX.), is 12 de- 
grees high, W. by N. ; and at the same elevation, 
more to the N., Mirach, in the girdle of Bootes 
(Plate VII), is observed. 

Alphecca Gemma, in the Northern Crown 
(Plate VII.), is 15 degrees high, between Bootes 
and Hercules ; and rather higher, towards the N., 
are the stars in the shoulders of Bootes. In the 
N. W., 50 degrees high, are the stars in the head 
of the Dragon (Plate III.). 

Charles's Heart (Plate III.) is 2 degrees high, 
N. W. by N. ; and the tail of the Great Bear 
(Plate IV) is seen some degrees above it. A line 
drawn from Alioth, in the tail, to the zenith, will 



162 CALENDAR OF THE STARS. 

pass the principal stars in the Dragon and the 
Great Bear. 

The Great Bear (Plate IV.) occupies the lowest 
part of the northern region. 



OCTOBER. 

Middle of the Month, about Ten o'clock. 

Castor and Pollux, in the Twins (Plate VI.), are 
just in the horizon, in N. E. ; and Orion in the E. 

Cap ell a and its companion, in the Charioteer 
(Plate VI.), are N. E. by E. ; the former 32 de- 
grees high, the latter 25. 

The foot of Castor is in the horizon, E. N. E. 
The N. horn of the Bull (Plate VI.) is more to 
the E., 23 degrees high ; Perseus (Plate IV.) is 
still higher ; and Cassiopeia (Plate IV.) near the 
meridian, 15 degrees below the zenith. 

Aldebaran, in the Bull (Plate VI.), is 23 de- 
grees high, due E. 

Algol, in the Head of Medusa (Plate IV.), 30 
degrees higher. 

The Pleiades (Plate VI.) are 37 degrees high. 

Menkar, in the mouth of the Whale (Plate 
XII.), about 33 degrees high, E. S. E. nearly. 

Arietis, the northern horn of the Ram (Plate V.), 
is 55 degrees high. 

Between the Ram and the Head of Medusa are 
the Triangles (Plate V), and the Fly (Plate V.). 

Mirach, in Andromeda (Plate V.), is 73 degrees 



CALENDAR OF THE STARS. 163 

high. Alpheratz, the head of Andromeda, is 78 
degrees high, very near the meridian. 

Algenib, in Pegasus (Plate V.), is about 62 de- 
grees high; Scheat and Markab have just passed 
the meridian. The whole of Pegasus extends from 
S. by E. to S. W. by S. 

Fomalhaut, in the Southern Fish (Plate XL), is 
S. by W. 

The Water-Bearer (Plate XL) is S. S. W. ; the 
star in his right shoulder is 44 degrees high, that 
in his left 28. 

, The principal stars in the Goat (Plate XL) are 
20 degrees high, S. W. 

The Dolphin (Plate IX.) is 44 degrees high, W. 
S. W. 

Altair, in the Eagle (Plate IX.), 30 degrees 
high, W. by S. 

The Swan (Plate III.) is nearly due W. AU 
biero, in its beak, 38 degrees high ; and Deneb, or 
Arided, 58. 

Vega, in the Lyre (Plate VII.), is nearly in the 
same altitude as Albiero, W. by N, 

Etanin, in the Dragon (Plate III.), 33 degrees 
high, N. W. 

The Great Bear (Plate IV.) is in the lower 
part of the N. 

Ras Algethi, in Hercules (Plate VII.) , and Ras 
Alhague, in the Serpent-Bearer, are just above 
the horizon, between W. by N. and W. N. W. 



164 CALENDAR OF THE STARS. 

NOVExMBER. 

Jlhout the Middle of the Month, at Ten o'clock. 

The Great Bear (Plate IV.) occupies the space 
included between the N. E. and N. Dubhe is N. 
N. E., 18 degrees high. In the same azimuth, 30 
degrees high, are the stars in the head. To the 
N. of N. E. is a star in the fore leg, in a line with 
Dubhe: and 14 degrees below 7 it, are two stars in 
the upper hind paw. The fore paws are in the 
N. E. 

The Little Lion (Plate IV.) is below the Great 
Bear, from N. E. to N. E. by N. 

The Cameleopard (Plate IV.) occupies the space 
above the Great Bear to the meridian. 

Castor and Pollux, in the Twins (Plate VI.), are 
E. N. E.; the first 22 degrees high, the last 18 
degrees high. 

More to the E. and at 45 degrees high, is the 
second star in the shoulder of the Charioteer 
(Plate VI.) ; and a few degrees higher is Capella, 
or Alioth. 

Nearly due E. are Procyon, in the Little Dog 
(Plate VI.), the feet of the Twins (Plate VI.), the 
Northern horn of the Bull (Plate VI.), and the 
constellation Prrseus (Plate IV.). 

Between rhe Charioteer, the Great Bear, the 
Little Lion, and the Twins, is the constellation 
Lynx (Plate VIII) 

Betelguex and Bellatrix, in the shoulders of 



CALENDAR OF THE STARS. 165 

Orion (Plate VI.), are seen about 28 degrees high, 
E. S. E. Rigel, in the heel, is 22 degrees high, 
S. E. by E. 

The Hyades, in the Bull (Plate VI.), are about 
45 degrees high, and the Pleiades about 59. The 
Hyades rise acronycally in the beginning of this 
month, as do also the Pleiades, which have been 
called the heralds of Winter. 

Two stars in the foot of Perseus (Plate IV.) are 
about 65 degrees high ; and Algol, in Medusa's 
Head, is about 75. 

The third star in the River Po (Plate XII.) is 
S. E. by S. 27 degrees high. 

Menkar, in the Whale (Plate XII.), is S. S. 
E. ; 50 degrees high, and the constellation extends 
to S. S. W. 

The Ram (Plate V.) is above the Whale ; and 
the stars in the head are nearly on the meridian. 

Alamak, in Andromeda (Plate V.), is in the 
zenith. 

Alpheratz, in the head of Andromeda (Plate V.), 
is S. W. 60 degrees high ; and the three conspicu- 
ous stars in Pegasus (Plate V.) are below it ; Al- 
genib is to the S., Scheat to the W., and Markab, 
the lowest, forming a triangle with the two last. 

The Fishes (Plate V.) are now visible ; one 
under Mirach, in Andromeda; the other under 
Markab, in Pegasus. 

The Water-Bearer (Plate XL) is S. W. by 
W. ; his water-pot is 25 degrees above the hori- 
zon, and 20 degrees below Markab. 
12 



166 CALENDAR OF THE STARS. 

Enir, in the mouth of Pegasus (Plate V.), is 30 
degrees high ; and below it is the Little Horse. 

The Dolphin (Plate IX.) is due W. 20 degrees 
high ; and the extremity of the wing of the Swan 
(Plate III.) is 20 degrees higher. 

The Eagle (Plate IX.) is near the horizon. 

The Swan is W. N. W. Mbiero, in the beak, 
is 15 degrees high; the third is 32 degrees high: 
Deneb, or Arided, is 37 degrees high; and the 
northern wing extends to N. W. 

Vega, in the Lyre (Plate VII.), is between N. 
W. by W. and N. W. 12 degrees high. 

Cepheus's shoulders (Plate HI.) are 44 and 54 
degrees high. 

Etanin, in the Dragon (Plate III.), is 15 de- 
grees high, N. W. by N. nearly; and the greater 
part of this constellation is between that star and 
the Little Bear, which is now below the Pole star. 



DECEMBER. 

Middle of the Month, about Ten o'clock. 

The body of the Little Bear (Plate III.) is 
upon the meridian, below the Pole star. A few 
degrees from it, towards the E., is seen the first 
star of the Dragon, 

The tail of the Great Bear (Plate IV.) is N. 
N. E. 

The Little Lion (Plate IV.) is between E. N. 
E. and N. E. bv E. 



CALENDAR OF THE STARS. 167 

Cor Leonis, or Regulus, in the Lion (Plate 
VIII.), is E. by N. about 8 degrees high; and 
more to the N. and higher, the stars in the head 
arid neck are seen; his paws are due E. 

The head of the Hydra (Plate XIV.) is due E. 
about 15 degrees high. A line drawn from it to 
Castor, in the Twins (Plate VI-), 45 degrees high, 
will pass the Crab (Plate VI.). Pollux is a few 
degrees below Castor. 

Procyon, in the Little Dog (Plate VI.), is be- 
tween E. S. E. and E. by S. 28 degrees high. A 
line drawn from this star to the zenith will pass 
near the feet of the Twins. Capella, in the Cha- 
rioteer (Plate VI.), is 15 degrees below the 
zenith. 

The UnicorxN (Plate VI.) is below Canis Minor. 

Sirius, in the Great Dog (Plate XIII.), between 
S. E. and S. E. by S. is about 20 degrees high. 
A line drawn from it to the zenith, at 48 degrees 
high, will pass near Betelguex in Orion's shoulder. 

Rigel, in Orion's heel (Plate VI.), S. S. E., is 
37 degrees high. 

The Hare (Plate XII.) is below Orion. 

Aldebaran, in the Bull (Plate VI.), is approach- 
ing the meridian : the Pleiades are on it. 

Perseus (Plate IV.) is in the zenith. 

The River Po (Plate XII.) occupies the south- 
ern region, extending from Orion to the Whale. 

Menkar, in the Whale (Plate XII.), is nearly 
52 degrees high, S. S. W. nearly ; his tail is S. W. 

A line drawn to the zenith will pass the head of 



168 CALENDAR OF THE STARS. 

the Ram (Plate V.) between the Triangles (Plate 
V.) and the Fly (Plate V.), and by the Head of 
Medusa (Plate IV.). 

Markab, in Pegasus (Plate V.), is nearly due W. 
25 degrees high. 

The head of Andromeda (Plate V.) is 46 degrees 
high ; Mirach, 61 ; Alamak, 72. 

Cassiopeia (Plate IV.) is between 50 and 60 
degrees, N. W. by W. 

Swan (Plate III.) is N. W. Deneb, or Arided, 
19 degrees high. 

The head of Cepheus (Plate III.) is 20 degrees 
higher ; and the whole of this constellation extends 
to the Pole star. 

The greater part of the Dragon (Plate III.) oc- 
cupies the space from N. N. W. to the Little 
Bear. 



SEC. 13. 

description of the plates of the telescopic 
appearance of the double stars. 

Fig. 1. a Geminorum or Castor. R. A. 110° 43', 
Dec. 32° 15'. This double star consists of 
two stars of the 3d and 4th magnitudes, of 
a greenish colour. Through ordinary tele- 
scopes they appear to be in contact, since 
their distance is only 5". In better tele- 
scopes they appear well divided. It has 
been found that these stars revolve round 
each other in a period of 232 years in an 



DESCRIPTION OF PLATES. 169 

elliptical orbit, whose greater axis is 14", 
and whose eccentricity is 0.8. 

Fig. 2. 7 Virginis. R. A. 188° 15', Dec. 0° 29', 
sosth. In this pair of stars also, both are 
of the 3d magnitude, and their distance is 
only 2". The period of their revolution is 
145 years in an elliptical orbit, of which the 
major axis is 7", and the eccentricity 0.9. 
These two stars appear in good telescopes 
as beautiful objects, sharply defined. Both 
stars are of a light yellowish colour. (See 
page 95.) 

Fig. 3. £ Ursae Majoris, or Mizar, the middle star 
in the tail of the Great Bear. R. A. 199° 
15', Dec. 55° 41'; of the 3d and 4th magni- 
tudes; distant 14". Easily divided with 
smaller telescopes. Both of greenish white. 

Fig. 4. a Herculis. R. A. 256° 30', Dec. 14° 36'; 
3d and 7th magnitudes ; distant 5". The 
greater bright yellow, and the smaller deep 
blue. 

Fig. 5. 7 Leonis ; 2d and 4th magnitudes ; distant 
2J". The greater gold yellow, the smaller 
greenish purple. The most splendid double 
star in the northern hemisphere, both in 
brightness and contrast of colours. 

Fig. 6. 7 Andromeda or Alamak. R. A. 28° 15', 
Dec. 41° 30'; 3d and 5th magnitudes; dis- 
tant 10". The greater orange, the smaller 
emerald green. The colours are very dis- 
tinct ; a beautiful object. 



170 DESCRIPTION OF PLATES. 

Fig. 7. j8 Ononis or Rigel. R. A. 76° 30', Dec. 
8° 25', south; 1st and 8th magnitudes; dis- 
tant 10 ". Colour yellowish white. 

Fig. 8. 7 Arietis or Mesarthim. R. A. 26° 0', 
Dec. 18° 27'; both of the 4th magnitude; 
distant 9" ; very white. 

Fig. 9. a Ursae Minoris or Polaris. For the year 
1844, R. A. 15° 45', Dec. 88° 20'; 2d and 
9th magnitudes; distant 18". The greater 
is yellow, the smaller white. 

Fig. 10. A double star, near the head of the south- 
ern Grey-hound. R. A. 181° 48', Dec. 41° 
36'; 5th and 8th magnitudes ; distant 11". 
The greater is a beautiful gold yellow, the 
smaller blue. 

Fig. 11. a Lyrse or Vega. R. A. 277° 45', Dec. 
38° 37'; 1st and 11th magnitudes; distant 
43". 



SEC. 14. 

PORTIONS OF THE HEAVENS RICH IN STARS. 

These are portions in which many stars appear 
to the naked eye, collected in a small space, which 
are not so dense as to be synonymous with clus- 
ters or groups of stars, in the strictest sense of the 
w T ord. 

Fig. 12. The Pleiades or the Seven Stars, called 
also the Clucking-hen, on the neck of the 



DESCRIPTION OF PLATES. 171 

Bull. With unassisted eyes we can distin- 
guish the larger stars of this collection. 

Fig. 13. The Hyades, upon the forehead of the 
Bull, of which the principal stars form a V. 

Fig. 14. The Crib in Cancer, or Proesepe, visible to 
the naked eye ; but through a telescope, even 
of small magnifying power, a very remarka- 
ble accumulation of many stars upon a space 
of about three-fourths of a degree square : 
midway between 7 and 8, or Asellus Borealis 
and Asellus Australis. 

Fig. 15. Another accumulation of stars, all large, 
between the ends of the Bull's horns, or be- 
tween /3 and g Tauri. The rings represent- 
ed in this figure with three or four small 
crosses, denote separate groups of stars or 
collections of many small and thickly clus- 
tered stars, which can only be recognised 
through very good telescopes, and of which 
an account will be found on the next page. 

Fig. 16. Another still more rich portion, in stars 
encompassing the whole constellation of 
Lyra. 

Fig. i7. This is likewise a spot, around the star 
Arcturus in Bootes, studded with many 
small stars. 

Fig. 18. Represents the neighbourhood of the re- 
markable nebula of Orion, abounding in 
small stars. 



172 DESCRIPTION OF PLATES. 

SEC. 15. 

CLUSTERS OF STARS. 

By this name is to be understood a great cluster 
of small stars, collected together upon a very small 
space, which are invisible to the naked eye, and, 
even with ordinary telescopes, appear only as a 
light cloud ; but resolvable, with more powerful 
telescopes, into small stars. Those parts of the 
heavens which, even through the most perfect 
telescopes, appear as light clouds, not resolvable 
into stars, are called nebulae. These last are con- 
tained in the next plate of this collection. It may 
here be remarked, that the number of these ne- 
bulae, many of which perhaps are nothing else 
than very distant groups of stars, is very great in 
some parts of the heavens. 

Fig. 19. In the northern wing of the Virgin is a 
space of 10° R. A. and Dec, which contains 
over a hundred such nebulas. The plate 
contains only the largest and most remark- 
able of the groups of stars. 
Fig. 20. A very rich group of stars, between v\ and 
s Herculis. R. A. 248° 45', Dec. 36° 48'. 
It is of an irregular form, scolloped, as it 
were, about the edge; and, although the 
stars of which it is composed appear more 
condensed toward the middle, yet the group 
has no proper nucleus. The number of stars 
in this group which are distinctly visible, 
exceeds a hundred ; but, towards the much 



DESCRIPTION OF PLATES. 173 

brighter middle, they are innumerable. — 
Those which are visible, are nearly all of 
the 9th to the 11th magnitudes. 

Fig. 21. A gorgeous group of stars in Berenice's 
Hair; the foregoing (Fig. 20) is not unlike it 
in the exterior form. R. A. 196° 0', Dec. 
19° 4'. Its apparent diameter is from 5 to 
6 minutes, and it contains a truly countless 
multitude of very densely-clustered stars, 
of the 10th to the 12th magnitudes. The 
elder Herschel pronounced this group the 
most gorgeous object which he had seen in 
the heavens. 

fig. 22. A large, round, beautiful group in Aqua- 
rius, almost entirely resolvable into stars, 
with very good telescopes. R. A. 321° 15', 
Dec. 1° 34', south. Toward the middle it 
appears very bright, and as it w r ere flaming, 
when viewed through the telescope. Ac- 
cording to the younger Herschel's expres- 
sion, it is like a globular heap of gold sand. 
The middle and brightest part of the whole 
is 6" in diameter, and is very similar to a 
star of the 6th magnitude. 

Fig. 23. A beautiful and very crowded group of 
stars in Libra, of a spherical form. R. A. 
227° 30', Dec. 2° 44'. Its light increases 
towards the middle very rapidly, and there 
the individual stars of which the group con- 
sists, cannot be separated. The diameter 



174 DESCRIPTION OF PLATES. 

of the whole is 2^', and the neighbourhood 
around this group is entirely void of stars. 

Fig. 24. The magnificent group of stars in Capri- 
cornus. R. A. 311° 0', Dec. 13° 13', south. 
It is round, and very brilliant. The stars 
are more crowded towards the centre, but 
with good telescopes can be separated. It 
contains more than a thousand fixed stars. 

Fig. 25. A large, fan-shaped, out-spread group of 
stars. R. A. 101° 18', Dec. 18° 14'. Towards 
the end, the light increases rapidly, and 
opposite this end the border appears torn 
and badly defined. Length and breadth of 
the whole, about 6'. 

Fig. 26. An elongated group, between a and A in 
the Crab, rounded on one side, and pointed 
upon the other. R. A. 129° 30', Dec. 13° 13'. 
The small, very much crowded stars appear 
as if lying about a light central body? and 
the whole group rests upon a nebulous 
ground. 

Fig. 27. A large, rich group of stars in Ophiuchus. 
R. A. 269° 10', Dec. 23° 50', south. It has 
an elliptical form, and nearly 30' length and 
5' width. Through good telescopes, it is 
resolvable into stars. 

STELLAR NEBULA. 

Under this name are included the nebulae which 
appear to abound with fixed stars. 
Fig. 28. A beautiful, round nebula, increasing in 



DESCRIPTION OF PLATES. 175 

light towards the middle ; at the centre of 
the nebula there is a single fixed star. This 
nebula stands south of /3 in the Great Bear. 
R A. 157° 0', Dec. 54° 24'. The diameter 
of the whole nebula is about a minute — that 
of the round, light nucleus, 15". 

Fig. 29. In Gemini. R. A. 109° 45', Dec. 21° 15'. 
A round, light nebula of 25" diameter, with 
a star of the 8th magnitude near its centre. 

Fig. 30. A long, bright, elliptical star nebula, in the 
Great Lion. R. A. 168° 33', Dec. 13° 55'. 
From the border toward the centre, the light 
increases very slowly at first; but, nearer 
the centre, it increases very rapidly. In 
the centre itself, the light is quite starlike. 
The apparent length of the nebula is 7', and 
the width 4'. 

Fig. 31. A very small, brilliant star, in a large, irre- 
gular, oval atmosphere, in Berenice's Hair. 
R. A. 190° 30', Dec. 26° 26'. 

Fig. 32. A long, narrow, spindle-shaped nebula, in 
the Great Lion. R. A. 167° 45', Dec. 14° 
32'. In the middle, where it becomes sud- 
denly bright, it appears to have a star. 
Length 15', width 1'. 

Fig. 33. A star of the 9th magnitude, with a light 
nebula attached to it, in the Unicorn. R. 
A. 97° 30', Dec. 8° 53'. The comet-like, 
nebulous tail is about 1' in length. 

Fig. 34. A very long, narrow, spindle-shaped nebu- 
lous streak, in Berenice's Hair. R. A. 187° 



176 DESCRIPTION OF PLATES. 

0', Dec. 26° 56'. In the middle is a star of 
the 9th magnitude. Length 15', width 30". 
Near and parallel to it, stands a smaller ne- 
bula of nearly the same form. 

Fig. 35. A star of the 9th magnitude, with a light, 
fan-like, nebulous tail, in the Unicorn. R. 
A. 97° 28', Dec. 8° 53'. Length and width 
of the tail, nearly 1'. The end of the tail 
appears not to touch the star, and the star 
appears faint and ill-defined. 

Fig. 36. A similar fan-shaped nebula in the Great 
Bear, in the extremity of which is a star of 
the 9th magnitude. R. A. 131° 45, Dec. 
54° 25'. There is also seen a very fine little 
star, clearly glistening through the nebula. 

Fig. 37. A small, faint, elliptical nebula, in the 
Greyhound. R. A. 192° 45', Dec. 35° 47'. On 
each end of the ellipse is a star of the 8th 
magnitude. 

Fig. 38. A long, spindle-shaped nebula in Pegasus. 
R. A. 344° 6', Dec. 1 1° 25'. Length 2', width 
20". The light regularly increases towards 
the middle. At each end is a star of the 
9th magnitude; but one of these is some- 
what out of the axis of the spindle. There 
are also seen, in the inner part of this nebu- 
la, three very fine little stars. 

Fig. 39. An elliptical nebula in Hydra, very sharp 
at each end. On each end is a small star — 
one of the 8th, the other of the 11th mag- 
nitude. R. A. 131° 27', Dec. 2° 25', south. 



DESCRIPTION OF PLATES. 177 

Fig. 40. A bright elliptical nebula in Sagittarius. 
R. A. 271° 45', Dec. 19° 56'. In each focus 
of the ellipse is a small star. The major 
axis of the ellipse is 50". 

Fig. 41. A round nebula, containing a triple star, 
in the Wagoner. R. A. 80° 3', Dec. 34° 7'. 
The triple star forms an equilateral triangle, 
whose side is 4" in length. The three stars 
are of the 8th, 9th and 10th magnitudes. 
Some observers pronounce the nebula itself 
not round, but an equilateral triangle (Fig. 
42), so that the position and form of the two 
triangles, formed by the nebula and by the 
three stars, bear a striking analogy to each 
other. 

DOUBLE NEBULA. 

As we have seen, above, double and multiple 

stars, so now we give double nebulae, which, owing 

to their respective positions, appear, at the first 

glance, to belong to each other. 

Fig. 43. A beautiful double nebula in the Twins. 

R. A. 108° 45', Dec. 29° 50'. The two equal, 

ound nebulas join one another, and both 

increase in light toward their centres, which 

are so bright that they shine almost like 

stars. A similar one stands in R. A. 225° 

0', Dec. 20° 32', in Bootes. 

Fig. 44. A double nebula in Berenice's Hair. R. 

A. 187° 0', Dec. 12° 8'. Both are round, and 

brighter towards the centres; but one is 



178 DESCRIPTION OF PLATES. 

considerably greater than the other. Their 
apparent diameters are 45" and 60". 

Fig. 45. Two round nebulae, nearly equal in mag- 
nitude, and similar to those in Fig. 43. R. 
A. 178° 15', Dec. 17° 55', south. They join 
each other, and are much brighter toward 
their centres. 

Fig. 46. An irregular double nebula, near z Ophiu- 
chi. R. A. 266° 0', Dec. 24° 30', south. In 
both these nebulae, we observe many fine 
stars. 

Fig. 47. Two elliptical nebulas in the Greyhound, 
pointed at their extremites. R. A. 188° 55', 
Dec. 33° 6'. The two ellipses are perpendicu- 
lar to each other, and joined at their extremi- 
ties. The greater is the brighter, and both 
increase in brightness towards the middle. 

HOLLOW NKBXJL2E. 

Fig. 48. The beautiful annular nebula in Lyra. 
R. A. 281° 45', Dec. 32° 49'. The outer 
diameter of the ring is 6". The interior 
opening is not quite so dark as the outer 
back-ground of the heavens, but appears 
filled by another fainter nebula. The whole 
has the appearance of a veil spread over a 
hoop, or ring. This nebula lies nearly mid- 
way between /3 and y Lyrae. 

Fig. 40. A very large, elliptical nebula in Perseus, 
with pointed ends. R. A. 33° 0', Dec. 41° 
34'. Its length is 4', and breadth 40". In 



DESCRIPTION OF PLATES. 179 

the middle we observe an elongated, dark 
space, and, at the ends of this dark space, 
two fine little stars. The whole is perhaps 
a circular nebulous ring, whose plane lies 
very obliquely to the sun or to the earth, so 
that it appears only in the form of a narrow 
ellipse. The form and position of the ne- 
bula are similar to those of the opening. 

Fig. 50. A three-branched nebula in Sagittarius. 
R. A. 268° 0', Dec. 23° 1', south. The ne- 
bula is divided into three branches, and at 
their point of junction there appears to be a 
large opening; the branches make angles of 
near 120° with each other. The diameter 
of the whole is nearly 7', and in the middle 
stand two large stars, one of which is a 
beautiful double star. 

Fig. 51. The great nebula in Charles's Oak. R. A. 
159° 0', Dec. 58° 40', near the star q of the 
Oak. This nebula, invisible in our country, 
has the form of a club, and we remark many 
stars dispersed in it. The nebula with stars 
seen in the figure over the Club, is a part 
of the Milky-way, which is very bright in 
that part of the heavens. 

IRRESOLVABLE AND PLANETARY NEBULjE. 

Most of the nebulas which have been thus far 
mentioned, are, with very good telescopes, resolv- 
able, either entirely or in part, into stars; so that 
they appear to us only as very far distant groups 



180 DESCRIPTION OF PLATES. 

of stars. The following, even when viewed through 
the most perfect telescopes, preserve their nebu- 
lous appearance. 

Fig. 52. The remarkable and great nebula in An- 
dromeda. R. A. 8° 15', Dec. 40° 20'. It 
has the form of a very eccentric ellipse with 
pointed ends, of which the major axis is 
nearly 30'. Its light increases towards the 
centre, at first slowly, then rapidly; still, it 
is not star-like at the centre, but presents a 
peculiar, strongly condensed, nebulous light. 
No part of this nebula is resolvable into 
stars, even with the most powerful tele- 
scopes; and it is without any trace of the 
scales, or flakes, and waves, which are so 
frequently observed in other nebulas. Yet 
w 7 e perceive many stars standing behind, 
and glittering through it. The nebula itself 
can be discerned, as a small cloud, even by 
the unassisted eye. It resembles a comet. 
Fig. 53. A nebula in the Whale, similar in form to 
that in Andromeda (Fig. 52.). R. A. 9° 46' 
Dec. 26° 13', south. A very extensive, long, 
bright, elliptic nebula, w r hich gradually in 
creases in brightness towards the middle. 
Fig. 54. An irregular nebulous streak nearxCygni, 
in the end of the western wing of the Swan. 
R. A. 309° 39', Dec. 30° 6'. It forms a very 
long streak, composed of several distinctly 
separated parts. Many portions of it are 
very light. This nebula is milky, without 



DESCRIPTION OF PLATES. 181 

unevenness of colour, and does not appear 
to be starry, although we see through it 
some isolated stars, which do not belong to 
it. The border of this nebula is in most 
parts faint. 

Under the name of Planetary Nebulae, are in 
general classed those round, sharply-defined discs, 
which in all parts throughout have the same de- 
gree of light, not increasing in brightness toward 
the centre, as in most of the foregoing examples. 
The surface of the mysterious heavenly bodies of 
this character, is covered with a fine, scaly, flaky 
light. 

Fig. 55. A planetary nebula in Sagittarius. R. A. 
293° 30', Dec. 14° 33', south. \ round, dimly 
lighted disc, of 10" diameter. Its light is 
in all parts the same, but not starry, though 
dusky and dispersed. Near it stand two 
stars of the 11th magnitude, like satellites 
of the nebula. 

Fig. 56. A planetary nebula in the northern hand 
of Andromeda. R. A. 349° 30', Dec. 41° 36. 
A beautiful, though dim, disc of 20" diame- 
ter. Its light is of a pale blueish colour. 
Near it stands a double star, of the 9th and 
10th magnitudes. 

Fig. 57. A planetary, elliptical nebula in Orion. 
R. A. 83° 15', Dec. 9° 0'. There is a similar 
one in the Fox, which has a diameter of 2"; 
13 



182 DESCRIPTION OF PLATES. 

and four small stars surround it, like so many 
satellites. 
Fig. 58. A large planetary nebula in the Great 
Bear. The disc is generally round, and 
throughout of the same degree of light. 
Diameter, 5'. Though not well defined, the 
light on the border appears suddenly to 
vanish. R. A. 166° 15', Dec. 55° 56'. We 
find a similar one in Bootes of extraordinary 
magnitude — R. A. 224° 4', Dec. 19° 6' — 
whose diameter is full 6'. The greatest ne 
bula of this kind is in the Swan ; R. A. 302 c 
15', Dec. 30° 2'. It has a diameter of nearly 
15'. 

OTHER REMARKABLE NEBULA. 

Fig. 59. The great and celebrated nebula in the 
sword-hand of Orion. R. A. 81° 45', Dec. 
5° 30', south ; near the star & Orionis, nearly 
four degrees below the middle of the three 
stars 6, s and £, lying in a right line, which 
are known by the name of Jacob's Staff. 
This, from its magnitude and beauty, and 
from the wonderful variety of its light, is 
the most remarkable of all the nebulae. One 
part of it is uncommonly bright, another 
cloudy and dim, and a third portion is quite 
dark, even to blackness. The dark parts 
are sharply divided from the bright ones. 
The many stars standing in this nebula 
shine very brightly, and appear to have a 



DESCRIPTION OF PLATES. 183 

remarkable covering. The appearance of 
the whole may be compared to the open 
mouth of an animal. 
Fig. 60. Likewise a very remarkable nebula in the 
constellation of the Fox. R. A. 298° 0', 
Dec. 22° 17'. It is generally elliptical in 
form, and near the extremities of the trans- 
verse axis, has two round spots, which are 
remarkable for their bright, uniform light ; 
whilst the other parts of the nebula faintly 
glimmer with a dusky light. The major 
axis of the ellipse is 8', and the circular 
spots are 3' in diameter. The light of this 
body is milky, and not resolvable; but four 
stars of the 9th to the 11th magnitudes are 
seen in it, which apparently do not belong 
to the nebula, but only shine through it. 

Fig. 61. A very remarkable nebula in the head of 
the Greyhound, six degrees below tne middle 
star £ in the tail of the Great Bear. At the 
centre it has a bright nucleus, which is sur- 
rounded at some distance from the border 
by a wide, light ring. Between this ring 
and the nucleus, lies a darker concentric 
ring. The diameter of the whole is 4j'. In 
one place the outer light ring is divided 
about one-third of the way round, so that 
it appears double for that distance. R. A. 
287° 37', Dec. 48° 5'. Near this stands a 
small round nebula, like a satellite. 



184 DESCRIPTION OF PLATES. 

Fig. 62. The Magellanic Clouds, which are also 
called the Cap-clouds and the Coal-sacks, 
are three dark spots in the bright part of 
the Milky- way by the Southern Cross. 
These dark spots, together, occupy a space 
of several degrees square, and they have 
their colour chiefly from the entire absence 
of stars in their neighbourhood. The great 
Magellanic Spot extends from R. A'. 185° 
15', to 196° 15', and from Dec. 61° to 64°, 
south, and lies between the Southern Cross 
and the Bee. The two other small Magel- 
lanic Spots are near together, in R. A. 160° 
0', and Dec. 62°, south, between the Cross 
and Charles's Oak. In Fig. 62, A is the 
Southern Cross; and B, B and B, are the 
three Magellanic Spots; and D and D 
are two groups of stars or bright nebulae, 
without the Milky-way. 



PART II. 

SEC. 1. 

GENERAL DESCRIPTION OF THE SOLAR SYSTEM. 

When we observe the heavens with attention, 
we occasionally find bodies which change their 
positions with regard to each other and to the 
fixed stars in their vicinity, being seen sometimes 
on the west, and at others on the east — sometimes 
above, and at others below — a certain fixed star; 
whilst the general configuration of the fixed stars 
composing any constellation in w T hich they may 
happen to be, remains the same from century to 
century. These moving bodies are called planets, 
from a Greek word signifying wanderers. Their 
motions, to an observer at the earth, appear, in 
many instances, exceedingly irregular, sometimes 
eastward, and at others westward ; and at times, 
also, they appear to be stationary. 

Ten bodies of this description have been disco- 
vered in the heavens. Five of these have been 
known in all ages; their names are Mercury, 
Venus, Mars, Jupiter and Saturn. The other 
five are hardly visible to the naked eye, and were 
unknown to the ancients. They have been disco- 
vered within the last seventy years, and their 
names are Vesta, Juno, Ceres, Pallas and Ura- 
nus. Besides these ten bodies, which, together 

(185) 



186 THE PTOLEMAIC SYSTEM. 

with the Earth, are called primary planets, the 
telescope has revealed to us four smaller bodies 
revolving around Jupiter, seven around Saturn, 
and six around Uranus; these, with our own 
moon, are denominated secondary planets. They 
are also called moons, or satellites. These thirty 
bodies, viz., the sun, the eleven primaries, and the 
eighteen secondaries, compose what is called the 
planetary, or solar system. 



SEC. 2. 

THE PTOLEMAIC SYSTEM. 

It was a long time before the true magnitudes 
and real motions of these bodies were ascertained. 
The ancients generally supposed the earth to be 
perfectly stationary in the centre of the universe, 
with the sun, moon and planets revolving about it 
in several nearly concentric heavens, or spheres, 
in the following order : the first, or lowest sphere, 
was that of the Moon, beyond which were those 
of Mercury, Venus, the Sun, Mars, Jupiter and 
Saturn — these being all within the sphere of the 
fixed stars. They found it a very difficult matter 
to reconcile the annual and daily motions of the 
sun, which are directly contrary to each other ; 
and still more difficult to account for the particu- 
lar course which each planet appeared to pursue. 
It required great ingenuity to invent machinery 
which would satisfactorily explain all the irregula- 



THE COPERNICAN SYSTEM. 187 

rities observed in the motions of the heavenly 
bodies. Solid spheres, cycloids, epicycloids, con- 
centric and eccentric circles, and a variety of 
other celestial machinery, were employed ; but 
without success. They never could account for 
the motions of Mercury and Venus, and the dif- 
ferent apparent magnitudes of the planets at dif- 
ferent times, without admitting a motion of the 
earth. 

The foregoing system is called the Ptolemaic 
System, from Ptolemy, an Egyptian astronomer, 
who first gave a full explanation of its details. It 
was generally received by the Greek philosophers, 
except Pythagoras and his followers, who main- 
tained the motion of the earth, and are supposed 
to have derived this knowledge from the ancient 
Egyptians. The Ptolemaic system held full sway 
over the minds of men, from the time of its author 
till near the middle of the sixteenth century. 



SEC. 3. 

THE COPERNICAN SYSTEM. 

This system, now known to be the only true 
one, was first promulgated about the middle of the 
sixteenth century. Its author, Nicolaus Coperni- 
cus, was a native of Thorn, in Prussia. His system 
at first met with much opposition, but w 7 as soon 
admitted to be the true hypothesis by the learned 
throughout Europe. In this system, the sun is 



188 THE COPERNICAN SYSTEM. 

considered as placed near the centre; and around 
this central luminary, the planets revolve in the 
following order of distances : Mercury, Venus, 
the Earth, Mars, Vesta, Juno, Ceres, Pallas, Ju- 
piter, Saturn and Uranus. 

It is now proved beyond all question that the 
earth is a planetary body, of a form very nearly 
spherical, revolving about its axis once every 
twenty-four hours, and about the sun once every 
year. 

In the earliest ages, the general opinion was 
that the earth was a vast extended plane; but astro- 
nomy had not made much progress before it was 
observed that the moon was frequently eclipsed 
by the earth's shadow, and that the form of this 
shadow, as seen upon the moon's disc, is always 
circular ; from which it necessarily followed that 
the earth, which casts the shadow, must be sphe- 
rical, since nothing but a sphere could in all posi- 
tions cast a circular shadow. 

When an eclipse of the moon happens, it is 
observed earliest by those who live farthest west ; 
which w T ould not be the case if the earth were a 
plane, since all would then see it at the same 
instant ; nor could the inhabitants of one part of 
the earth enjoy the light of the sun, while those 
of another part were deprived of it. 

The rotundity of the earth in an easterly and 
westerly direction, is demonstrated by its having 
been several times circumnavigated, or sailed 
around, in that direction. These voyages might 



THE COPERNICAN SYSTEM. 



have been performed in one direction, if the earth 
had been of a cylindrical form ; but such cannot 
be the case; for, when a ship, in any part of the 
world, departs from the coast in any direction, the 
persons on board first lose sight of those objects 
near the level of the sea, then of the more elevated 
portions of the coast, and lastly of the high towers 
and mountains. In sailing northward, the stars 
in the northern part of the heavens will become 
more elevated; whilst those in the south will gra- 
dually approach the horizon, and become invisi- 
ble. These arguments clearly prove that the 
general figure of the earth is spherical; but, as 
w r ill be seen hereafter, it deviates a little from a 
perfect sphere, being slightly compressed or flat- 
tened at the poles. 

It has already been shown, in the first part of 
this work, that the aspect of the heavens at every 
instant, as referred to the horizon of a spectator 
upon the surface of the earth, w T ill be the same, 
whether the earth remains at rest, while all the 
heavenly bodies revolve about it once in twenty- 
four hours ; or whether the spectator is carried 
about in the opposite direction, and in the same 
space of time, by a revolution of the earth. If 
the former supposition were correct, the near- 
est fixed star whose distance is now known, 
would have to move with the inconceivable ve- 
locity of more than three thousand millions 
of miles per second, which is fifteen thousand 
times the velocity of light, and more than three 



190 DEFINITIONS. 

thousand millions of times greater than that 
of a cannon-ball. The improbability, if not the 
impossibility, of such a rate of motion, is a suffi- 
cient argument against the supposition of the 
rotation of the stars about the earth; and as there 
is no other alternative, we must admit the diurnal 
revolution of the earth to be the cause of the ap- 
parent diurnal motion of the heavens. 

All the planets seem to have a motion some- 
times direct — that is, from west to east ; sometimes 
retrograde — that is, from east to west; and, at 
other times, they appear for a short period to be 
stationary in the heavens, or to have no motion at 
all. These appearances cannot be supposed to be 
the real motions of the planets ; and they can only 
be explained by the hypothesis of Copernicus, that 
the earth, in common with all the other planets, 
revolves around the sun : they are the necessary 
consequences of this system. 



SEC. 4. 

DEFINITIONS. 

Planets are opaque bodies, similar to our earth, 
which move round the sun in certain periods of 
time. They shine not by their own light, but by 
the reflection of the light which they receive from 
the sun. The planets are distinguished intojon- 
mary and secondary. 



DEFINITIONS. 191 

The Primary Planets regard the sun as their 
centre of motion. There are 11 primary planets, 
distinguished by the following characters and 
names, viz. : 5 Mercury, 9 Venus, © the Earth, 
c? Mars, a Vesta, Juno, J Ceres, $ Pallas, 
*2l Jupiter, h Saturn, and W Uranus. 

The Secondary Planets, satellites, or moons, 
regard the primary planets as their centres of mo- 
tion : thus the moon revolves round the earth, the 
satellites of Jupiter move round Jupiter, &c. 
There are 18 secondary planets. The earth has 
one satellite, Jupiter four, Saturn seven, and Ura- 
nus six. 

The Orbit of a planet is the imaginary path it 
describes round the sun. The earth's orbit is in 
the plane of the ecliptic. 

The Zodiac is an imaginary belt surrounding the 
heavens, extending 8° on each side of the ecliptic. 
It is divided into 12 signs of 30° each, which are 
reckoned from the vernal equinox eastward. 

Nodes are the two opposite points where the 
orbit of a planet seems to intersect the ecliptic. 
That where the planet appears to ascend from the 
south to the north side of the ecliptic, is called the 
ascending, or north node, and is marked thus Q ; 
and the opposite point, where the planet appears to 
descend from the north to the south, is called the 
descending, or south node, and is marked {3. 

Aspect of the stars or planets is their situation 
with respect to each other. The aspects are : 
c5 Conjunction^ when they are in the same sign and 



192 DEFINITIONS. 






degree ; d Quartile, when they are three signs, or 
a fourth part of a circle apart ; 8 Opposition, when 
they are six signs, or half a circle, from each other. 

The conjunction and opposition (particularly of 
the moon) are called the Syzygies ; and the quar- 
tile aspect, the Quadratures. 

Direct. A planet's motion is said to be direct 
when it appears (to a spectator on the earth) to go 
forward in the zodiac, according to the order of 
the signs. 

Stationary. A planet is said to be stationary, 
when (to an observer on the earth) it appears for 
some time in the same point of the heavens. 

Retrograde. A planet is said to retrograde, 
when it apparently goes backward, or contrary to 
the order of the signs, 

Digit, the twelfth part of the sun or moon's 
apparent diameter. 

Disc, the face of the sun or moon, or of a planet, 
such as they appear to a spectator on the earth ; for, 
though the sun, moon and planets are really sphe- 
rical bodies, they appear to be circular planes. 

Geocentric latitudes and longitudes of the pla- 
nets, are their latitudes and longitudes as seen 
from the earth. 

Heliocentric latitudes and longitudes of the 
planets, are their latitudes and longitudes as they 
would appear to a spectator situated in the sun. 

Apogee, or Apogeeum, is that point in the orbit 
of a planet, the moon, &c, w T hich is farthest from 
the earth. 



DEFINITIONS. 193 

Perigee, or Perigaeum, is that point in the orbit 
of a planet, the moon, &c, which is nearest to the 
earth. 

Aphelion, or Aphelium, is that point in the 
orbit of the earth, or of any other planet, which 
is farthest from the sun. This point is called the 
higher Apsis. 

Perihelion, or Perihelium, is that point in the 
orbit of the earth, or of any other planet, which 
is nearest to the sun. This point is called the 
lower Apsis. 

Line of the Apsides is a straight line joining 
the higher and lower apsides of a planet, viz. : a 
line joining the Aphelium and Perihelium. 

Eccentricity of the orbit of any planet is the 
distance between the sun and the centre of the 
planet's orbit. 

Occultation is the obscuration or hiding from 
our sight any star or planet, by the interposition 
of the body of the moon, or of some other planet. 

Transit is the apparent passage of any planet 
over the face of the sun, or over the face of an- 
other planet. Mercury and Venus, in their tran- 
sits over the sun's disc, appear like dark specks. 

Eclipse of the Sun is a partial or complete 
occultation of part of the face of the sun, occa- 
sioned by an interposition of the moon between 
the earth and the sun; consequently, all eclipses 
of the sun happen at the time of new moon. 

Eclipse of the Moon is a partial or complete 



194 DEFINITIONS. 

privation of the light of the moon, occasioned by 
an interposition of the earth between the sun and 
the moon ; consequently, all eclipses of the moon 
happen at full moon. 

Elongation of a planet is the angle formed by 
two lines drawn from the earth, the one to the 
sun, and the other to the planet. 

Diurnal Arc is the arc described by the sun, 
moon, or stars, from their rising to their setting. 
The sun's semi-diurnal arc is the arc described in 
half the length of the day. 

Nocturnal Arc is the arc described by the sun, 
moon, or stars, from their setting to their rising. 

The Elements of the orbit of a planet are six in 
number, viz. : 

1. The time of passing the perihelion or aphe- 
lion, or the mean longitude for a particular date. 

2. The mean distance or semi-major axis, or the 
daily siderial motion. 

3. The eccentricity. 

4. The longitude of the perihelion or aphelion. 

5. The longitude of the ascending node. 

6. The inclination of the plane of the orbit to 
the plane of the ecliptic. If this is considered to 
be always less than 90°, it must also be stated 
whether the motion is direct or retrograde. 



kepler's laws. 195 



SEC. 5. 

kepler's laws. 

First Law. 

Kepler ascertained, by direct observation, that 
the planets all describe ellipses round the sun, the 
latter being situated, not in the centre, but in one 
of the foci of the curve ; and it has since been 
found that several comets move in ellipses : it is 
highly probable that they all describe paths of the 
same kind around the sun, although they are so 
much elongated as not to be distinguishable from 
the parabola, by observations upon them, during 
the short time they remain within the reach of our 
telescopes, which is at most but a few months; 
while many of them require thousands of years to 
complete a revolution. 

Definition.— The ellipse is a curve, of an oval 
or elongated form, all points of which lie in the 
same plane. The longest diameter of an ellipse 
is called the major, or transverse axis ; it divides 
the curve into two equal parts. The foci are two 
points in the transverse axis, equally distant from 
the centre ; if from any point of the curve two 
lines be drawn to the two foci, their sum will be 
equal to the transverse axis. Since the sun is in 
one of the foci of the elliptical orbit of a planet, 
the latter will at different times be at unequal 
distances from the sun. The line joining the cen- 



196 KEPLER S LAWS. 

tres of the sun and planet, at any time, is called 
the radius vector. 

This law was discovered by Kepler, by his observations of 
the orbit of Mars, which, fortunately for science, is the most ec- 
centric of all the orbits of the planets then known, except Mer- 
cury. This law has been, since Kepler's time, farther gene- 
ralized ; and, instead of an ellipse, it has been found that the 
orbit of one body round another central body, may be any 
conic section having the central body in its focus. The two 
bodies may be either the sun and a planet, or the sun and a 
comet, or a planet and its satellite. 

By a conic section is meant the curve formed by the outline 
of the section of a cone. If this section is made perpendicu- 
larly to the axis of the cone, the curve will be a circle. If 
the plane of the section be slightly inclined to the axis, the 
curve becomes an ellipse having two foci equidistant from the 
centre. The distance by which the centre is removed from 
either focus, is called the eccentricity. If the section is made 
parallel to the surface of the cone, the curve never closes, 
except on the side where the section commences. In this 
case, the centre is at an infinite distance, and the curve is 
called a parabola, which is in reality the same as an ellipse 
with the long axis infinitely great. If the section is still 
more inclined to the axis, the curve is called a hyperbola, 
with the imaginary centre removed in the contrary direction, 
so as to be outside of the point where the section com- 
mences. 

Kepler 9 s Second Law. 

Kepler also discovered that the radius vector 
of a planet describes equal areas in equal times; 
that is, if radii vectores be drawn from the sun to 
those points of the orbit occupied by the planet at 
any equal intervals of time, the areas of the spaces 
included between any two of these lines which 



kepler's laws. 197 

are adjacent to each other, will be equal — although 
the planet moves much more rapidly in one part 
of its orbit than in another, the greatest velocity- 
being when it is nearest the sun, and the least 
when it is most distant. The velocity decreases 
as the radius vector increases. 

This property of the orbital motion of the planets may be 
illustrated by a very simple experiment, as follows : Tie a 
small leaden ball to a fine string, and, having whirled it round 
with a moderate velocity in a vertical plane, allow the string 
to coil itself round the finger, held firmly in a horizontal po- 
sition. The ball will then gradually approach the centre of 
motion in a spiral line, and the corresponding increase in its 
angular velocity will show clearly the compensation by which 
equal areas are described in equal times under a constantly 
diminishing distance of the body from the centre of motion. 
If the motion be reversed, and the thread allowed to unwind 
itself, by giving the ball a sudden impulse, the angular mo- 
tion will be at first rapid, but will gradually diminish as the 
distance of the ball from the centre of motion increases. 

Kepler's Third Law. 

In comparing the distances of the planets from 
the sun, with their periods of revolution, we find 
that, the greater the distance, or the larger the 
orbit, the longer is the time occupied in making a 
revolution. Kepler discovered that the squares 
of the periodic times of any two planets are propor- 
tional to the cubes of their mean distances from the 
sun. Take, for example, the Earth and Mars,^ 
whose periods are 365.2564 and 686.9796 days, 
and whose distances from the sun are in the pro- 
14 



198 NEWTONIAN THEORY OF GRAVITATION. 

portion of 1 to 1.52369 ; and it will be found that 
(365.2564) 2 : (686.9796) 2 : : (l) 3 : (1.52369) 3 . 

The mass of the earth being far smaller than that of the 
sun, the moon describes a proportionally smaller area round 
it in a moment of time. So, Uranus, Saturn and Jupiter 
having greater masses than the earth, their satellites make 
greater areasround their primaries, in a moment of time, than 
our moon does round the earth. Still, the third law of Kepler 
prevails in each secondary system. Among the satellites of 
the same system, the squares of the periodical times are always 
as the cubes of their mean distances from the primary of the 
system. 



SEC. 6. 

THE NEWTONIAN THEORY OF GRAVITATION. 

Though Kepler had discovered the three re- 
markable laws that regulate the motions of se- 
condaries round their primaries, and of primaries 
round the sun, still the cause of the prevalence of 
this law was unknown. This discovery was re- 
served for Sir Isaac Newton, and is justly consi- 
dered the greatest discovery ever made by an 
uninspired man. 

Newton found that the force which makes an 
apple fall from a tree to the ground, makes the 
moon revolve round the earth in an elliptic orbit. 
This force, which is called gravity, or the attrac- 
tion of gravitation, extends its influence, not 
merely from the earth to the moon, but to the sun, 
and to the other planets and satellites, and doubt- 



NEWTONIAN THEORY OF GRAVITATION. 199 

less to every star and nebula in the universe. 
This force of gravity of any two particles of mat- 
ter diminishes as the square of their distance from 
each other increases. Two particles of matter so 
close to each other as to form parts of the same 
solid or fluid, exert upon any third particle not in 
contact with them, twice as much force of attrac- 
tion as one particle could do. And, generally, the 
force of attraction in any system of particles, or 
bodies, increases directly as the number of similar 
attracting particles, or, in other words, as the mass 
of the system, increases. 

There never was a law of such vast importance 
announced in so few words. The simple princi- 
ple, that gravity varies directly as the mass, and 
inversely as the square of the distance, enables us 
to infer ct priori all of Kepler's laws. If one of 
several bodies of a system moves round the com- 
mon centre of gravity of that system by virtue of 
this law, it will move in a conic section according 
to the first law ; its radius vector will describe 
equal areas in equal times, according to the second 
law; and if we take the time of a complete revo- 
lution of any one of the bodies of the system as 
a unit of time, and its mean distance from the sun 
as the unit of distance, then the time in which any 
body in the system will complete its orbit, will be 
equal to the square root of the cube of the mean 
distance of that body. 

Again, if we know the masses of any of the 
secondary systems, compared with that of the 



200 NEWTONIAN THEORY OF GRAVITATION. 

solar system, we can determine the periods of the 
satellites at any supposed distance from the centre 
of gravity of such secondary system. The power 
of causing areas to be described will be directly 
as the masses of the two systems, where the dis- 
tances are the same ; and, for different distances, 
the periods may be ascertained by Kepler's third 
law, as above. 

The Newtonian law of gravity is found to ex- 
tend to most of the stellar systems, and doubtless 
prevails throughout the universe. If this be ad- 
mitted, the masses, mean distances, and periods 
of any one of the stars in a binary or multiple 
stellar svstem are connected together bv such a 
law, that, if any two of them are known, the third 
follows of course. It was in this way that Bessel, 
having found the distance of the stellar system 61 
Cygni, and knowing its period before, was enabled 
to determine the mass of this stellar system, which 
he found to be about two-thirds that of our own. 
In the appendix will be found Maedler's factor for 
the masses of the several stellar systems whose pe- 
riods of revolution are known. When the paral- 
lax of any of these systems is known, this factor 
must be divided by it, and afterwards cubed, 
in order to obtain the mass of the system. The 
research after the parallax and distance of the 
fixed stars on BessePs plan, is still in its infancy. 
It cannot be doubted that, in the progress of time, 
perhaps in a single century, the distances and 
consequent masses of many of the stellar systems 



THE SUN. 201 

will be ascertained, so as to afford a classification 
of the fixed stars according to their quantity of 
matter. If this shall ever be accomplished, and a 
general average is found to prevail in the masses 
of stars, as has been shown to be probable, in 
reference to their brightness and distance asunder, 
then an estimate may be formed of the quantity 
of matter in the universe, or rather in that portion 
of universal space which we are capable of ex- 
pressing by finite symbols. 



SEC. 7. 

THE SUN, 

The glory of our system, and the agent by which 
the great Creator dispenses light and heat to the 
surrounding planets, was, in the infancy of astro- 
nomy, reckoned among the planets ; but it is now 
numbered among the fixed stars. He appears, 
indeed, bright and large in comparison with them ; 
but this is only because we are so much nearer to 
him ; for a spectator placed as near to any star as 
we are to the sun, would see a body as large and 
bright in that star as the sun appears to us ; while 
the sun, on the contrary, viewed from the same dis- 
tance as that of the nearest fixed star from us, would 
assume the appearance of a star, and his attendant 
planets would be invisible. Although we thus 
speak of the nearness of the sun to the earth, it 
must be kept in mind that the expression is used 



202 THE SUN. 

only in a relative sense ; for his distance from the 
earth amounts in round numbers to about 95,000,- 
000 miles; and a cannon-ball, moving at the rate of 
about eight miles in a minute, would occupy more 
than twenty-two years in traversing the interven- 
ing space. In this respect, therefore, the sun is 
at a very great distance from the earth ; but when 
it is known that the distance of the nearest fixed 
star is six hundred thousand times that of the sun, 
and that a cannon-ball, moving at the rate already 
supposed, would not pass thence to the earth in 
less than 1,000,000 years, the sun may well be 
said to be comparatively near. 

The figure of the sun is that of a spheroid, higher 
under the equator than about the poles His dia- 
meter is computed at about 890,000 miles, his cir- 
cumference about 2,700,000 miles, and his bulk up- 
wards of a million of times greater than that of 
our earth. The sun revolves upon its axis from 
east to west once in 25 days 14 hours 8 minutes; 
the axis being inclined to the ecliptic at an angle 
of 82^ degrees. The north pole of the sun's axis 
is directed nearly towards <k Draconis, and its 
southern pole towards a point midway between a 
and /3 of the Ship. It has also a periodical motion, 
in nearly a circular direction, round the common 
centre of all the planetary motions, never deviat- 
ing from its position by more than twice its dia- 
meter. 

The sun was long believed to be an immense 
globe of fire ; but some philosophers are of opinion 



THE SUN. 203 

that, like the earth, it is a cold, opaque, and habi- 
table globe, surrounded with a luminous phosphoric 
atmosphere, which diffuses light through the whole 
system. Sir William Herschel supposed that the 
lucid matter of the sun exists in the manner of 
luminous clouds, swimming in his transparent 
atmosphere ; and he considered that there are two 
different regions of solar clouds, and that the lower 
region consists of clouds less bright than those 
which compose the upper stratum. The removal 
or opening of these clouds, he supposed, exhibits 
the opaque globe of the sun to our view ; and 
hence those dark spots, or maculce, which from 
time to time are visible upon his disc. The facu- 
Ice, or bright spots, as he supposed, are caused by a 
decomposition of the transparent and elastic fluids 
by which the sun is surrounded ; and lucid ap- 
pearances are thus formed of various degrees of 
intensity. By observations of these spots, the 
revolution of the sun upon its axis has been ascer- 
tained. 

Besides the solar spots, the zodiacal light is a 
singular phenomenon which accompanies the sun. 
It begins to be visible, in the fall, a little before 
sunrise, appearing at first like a faint whitish zone 
of light, somewhat resembling the galaxy, or 
milky-way, with its borders ill-defined, and 
scarcely to be distinguished from the twilight, 
which is seen commencing near the horizon. It 
is then but a little elevated, and its figure agrees 
with that of a lens turned edgewise towards us. 



204 THE SUN. 

As it rises above the horizon, it becomes brighter 
and larger, to a certain point ; after which, the 
approach of day renders it gradually less appa- 
rent, till it becomes quite invisible. It appears 
in the west, after sunset, in December and for 
several months afterwards. It is supposed to be 
of a lenticular shape, having the sun near its cen- 
tre, like the nebulous stars occasionally seen in 
telescopes. It is difficult to comprehend how the 
particles of matter composing it (if it be material) 
maintain their position. Perhaps they are in a 
state of revolution round the sun, like the meteors 
which the earth encounters in its yearly motion. 
Professor Olmsted has suggested the idea that the 
periodical meteors of November 12th, 1833, were 
a portion of this zodiacal light. 

The force of gravity at the surface of the sun is 
much greater than with us. A body weighing 1 
pound at the earth's surface, w 7 ould weigh 28 
pounds 5f ounces at the sun's ; and a heavy body 
near the sun's surface would fall 456.41 feet in 
the first second of time. The physical power of 
our strongest men would hardly enable them to 
move themselves upon the sun ; for a man here, 
weighing 150 pounds, would there weigh more 
than 4200 pounds. If the sun's surface is inhabit- 
ed, it must be by beings very differently organized 
from those on the earth. 

It must be recollected, that if we could carry 
the same steelyards to the sun, a pound here would 
weigh a pound there, the counterpoise having in- 



THE SUN. 205 

creased its gravity as much as the object weighed. 
A true test would be the elastic force of a spring, 
or coil. 

The sun, in common with the twenty-nine pla- 
nets and secondaries, has a proper motion in 
space, estimated by Struve to be half as great as 
the linear velocity of our earth in its orbit, or 
about eight miles per second, towards the constel- 
lation of Hercules. The point of tendency is in 
R. A. 259°, Dec. 35°, being about a degree north- 
east of the small star u Herculis. This point 
seems to vary its position slowly in the heavens, 
indicating a change in the tangential direction of 
our system, or, in other words, a curvilinear or 
orbital motion round some centre of attraction at 
present unknown. The proper motions of many 
of the stars were observed by Halley, Lemonnier, 
Cassini and Mayer. The latter suggested the true 
cause of this apparent motion ; but Sir Wm. Her- 
schel first pointed out the true quarter of the hea- 
vens towards which the motion is now directed. 
Argelander has tested this point by all the stars 
known to have a proper motion, and finds a full 
confirmation. Struve, at Pulkovah, has recently 
endeavoured to form an estimate of the quantity 
as well as the direction of this motion. The ura- 
nographical effect of it is to enlarge the relative 
distances of the stars in the constellation of Her- 
cules, and to compress together those which are 
in its antipode. 

Among the ancients, the sun was an object of 



206 MERCURY. 

idolatry, under various names, as Ham or Cham, 
Chemosh, Zamos, Osiris, Vulcan, Sol, Phoebus, 
Apollo, &c. ; and was considered as the god of 
day, the dispenser of light, heat, and fertility, and 
the good principle with which darkness, or evil, 
w T ould wage continued warfare till the final con- 
summation, when light, or goodness, should even- 
tually triumph. His symbol, fire, was maintained 
with the utmost care upon the heathen altars, and 
even participated in the worship paid to him. 

The astronomical sign for the sun O is the peri- 
phery of a circle with a central point, indicative 
of the central situation of the luminary with re- 
spect to the solar system. 



SEC. 8. 

5 MERCURY, 

The first planet in the solar system, and the 
nearest to the sun, performs his revolution about 
that luminary in 87 days 23j hours, nearly, which 
constitutes the length of his year. His rotation 
upon his axis has been stated at 24 hours 5j mi- 
nutes, which would constitute the length of his 
day; but as no spots by which to determine it 
have yet been observed upon his face, this is un- 
certain. 

The distance of Mercury from the sun is about 
37,000,000 of miles, and he moves in his orbit at 



MERCURY. 207 

the amazing rate of upwards of 95,000 (or, accord- 
ing to some astronomers, 105,000) miles an hour. 
His diameter is about 3,000 miles, or somewhat 
more than one-third of that of the earth. Though 
small, Mercury has a bright appearance, with a 
bluish tint. 

The orbits of Mercury and Venus are within 
that of the earth. They are therefore called infe- 
rior planets. The other planets, w ? hose orbits are 
without that of the earth, are called superior pla- 
nets. The inferior planets can never be in oppo- 
sition ; that is, they can never be in the part of 
the heavens opposite the sun ; but will always be 
seen near the sun. They sometimes pass between 
the sun and the earth ; this aspect is called their 
inferior conjunction. At other times they will ap- 
pear in the direction of the sun, but beyond him; 
they are then in their superior conjunction. 

Mercury never departs more than 30° from 
the sun, and can rarely be seen without a telescope. 
When seen in a telescope, he exhibits the various 
phases of the moon, or of Venus (see the drawing 
for Venus), except that he cannot be seen at the 
full, on account of the interposition of the sun at 
that time. 

The following drawing represents the transits 
of Mercury for the rest of the century : 



208 



MERCURY. 



NORTH. 




SOUTH. 

When the inferior conjunction occurs at the 
same time that the planet is in one of its nodes, it 
passes over the sun as the moon does in solar 
eclipses. This phenomenon is called a Transit 
of Mercury. On account of the small relative 
diameter, only a small portion of the sun's disc is 
eclipsed. For a long series of centuries, this 
transit can only happen in the months of May and 
November. It was observed for the first time in 
November, 1631, by GassendL The following is 
a list of all the transits of Mercury from 1631 to 



MERCURY. 209 

the end of the nineteenth century. See the draw- 
ing. 

1631 Nov. 6. 1776 Nov. 2. 

1644 Nov. 8. 1782 Nov. 12. 

1651 Nov. 2. 1786 May 3. 

1661 May 3. 1789 Nov. 5. 

1664 Nov. 4. 1799 May 7. 

1674 May 6. 1802 Nov. 8. 

1677 Nov. 7. 1815 Nov. 11. 

1690 Nov. 9. 1822 Nov. 4. 

1697 Nov. 2. 1832 May 5. 

1707 May 5. 1835 Nov. 7. 

1710 Nov. 6. 1845 May 8. 

1723 Nov. 9. 1848 Nov. 9. 

1736 Nov. 10. 1861 Nov. 11. 

1740 Nov. 2. 1868 Nov. 4. 

1743 Nov. 4. 1878 May 6. 

1753 May 5. 1881 Nov. 7. 

1756 Nov. 6. 1891 May 9. 

1769 Nov. 9. 1894 Nov. 10. 

The phases of this planet prove that it does not 
shine by any inherent light; for in that case it 
would always appear round. 

It is the most dense of all the planets, being 1 J 
times as dense as the earth. Its mass is about 
one eight-hundred-thousandth of that of the sun. 

Owing to the great eccentricity of the orbit of Mercury, its 
year of 86| solar days is divided into seasons of very unequal 
length ; but since we have no knowledge respecting the direc- 
tion of its axis, we can have no precise information concern- 
ing its seasons. Another consequence of this great eccen- 



210 MERCURY. 

tricity is, that its days are very unequally lighted : in the peri- 
helion the light from the sun is 11 times, and in the aphelion 
only 5 times, as intense as with us ; and the apparent diame- 
ter of the sun is in the former case 1° 39' 21".3, in the latter 
only 1° 8' 34". 0. The day is, moreover, about 15 minutes 
longer when the planet is in its perihelion, than when in its 
aphelion. 

Mercury can never experience an eclipse, nor can there 
ever occur, for it, a transit of another planet over the disc of 
the sun, unless there be a planet yet undiscovered whose orbit 
is within that of Mercury. All the other planets will at cer- 
tain times be in opposition to this one, and the apparent daily 
motion of these and of the fixed stars is nearly as rapid as for 
the earth. Venus appears from Mercury about 12 times as 
brilliant, at a maximum, as from the earth ; it may, therefore, 
in some measure, supply the want of a moon. The earth, as 
seen from this planet, is large and brilliant, and our moon 
appears as bright to them as Mars does to us. This last is 
considerably fainter there than here. For the other planets, 
there is no very essential difference whether seen from Mer- 
cury or the earth ; except that, in the former case, all the 
retrograde motions are confined to a much smaller arc, and to 
a shorter time. None of the bodies of the system present to 
it any perceptible phases. 

One pound at the earth, has the weight of 9J 
ounces at Mercury ; the fall of a body in the first 
second of time is 9 J feet ; and the length of a pen- 
dulum vibrating seconds is 1.89 feet. These mag- 
nitudes are probably nearly the same for all parts 
of the globe, as no compression has yet been de- 
tected, and the rotation, considered as linear, is 
very slow. 

Mercury was considered by the mythologists as 
the messenger of the gods, and was called Hermes, 



VENUS. 



211 



Hermes Trismegistos, Thoth, Taut, &c. The 
astronomical sign of this planet $ is supposed by- 
some to represent the caducens with which the 
heathens furnished Mercury : it consisted of a 
sceptre entwined by two serpents in the form of 
two equal semi-circles, and winged at the top. 



SEC. 9. 

9 VENUS, 

The second planet from the sun, from which 
she is distant somewhat more than 69,000,000 of 
miles, moves at the rate of between 75,000 and 
80,000 miles per hour, and completes her annual 
revolution in 224 days 16f hours, nearly, and her 
diurnal rotation in rather less than 24 hours.* 
Her magnitude is nearly the same as.that of the 
earth ; her diameter being about 7630 miles. The 
circumference of her orbit is at least 433,000,000 
of miles. 

Venus is easily distinguished by her silver-white 
appearance, and by surpassing *iti brightness all the 
other stars and planets. She is sometimes so bril- 
liant as to be seen in full day by the naked eye. 
This phenomenon arises from her very dense at- 

* Sir Wm. Herschel, after repeated observations, could not 
satisfy himself as to the rotation of Venus on her axis. Bian- 
chini gives it the incredible term of 24 days 8 hours ; but 
Cassini reduces it to 23 hours 20 minutes, and Schrceter to 
23 hours 21 minutes. 



212 VENUS. 

mosphere, which is capable of exhibiting reflec- 
tions. She has phases, like the moon; and the 
time of her greatest brightness is when she ap- 
pears in the crescent form. At this season she 
presents a more pleasing telescopic view than any- 
other of the heavenly bodies. Her surface is di- 
versified with spots ; and by the motion of these 
we ascertain the time she occupies in revolving 
upon her axis. 

Venus appears much larger at one time than at 
another; and the great variations of her apparent 
diameter demonstrate her distance from the earth 
to be extremely variable. See the drawing. 

This figure shows Venus at her inferior conjunction atlas 
a new moon, at her greatest eastern elongation; as evening 
star at E, as a half-moon of medium size ; at her superior 
conjunction at S, as a small full moon; and at her greatest 
elongation as morning star at W. 

In her seasons, also, she must experience a 
much greater difference than is known upon our 
earth ; for her axis inclines about 75 degrees to the 
plane of her orbit, and at her equator she must 
have two springs, two summers, as many autumns, 
and two winters, in each year. 

This planet is a constant attendant upon the 
sun, from which she never removes more than 48 
degrees, and consequently is never seen at mid- 
night, nor in opposition to that luminary, being 
visible only for three or four hours in the morning 
or evening, according as she is before or after the 
sun. When she rises before the sun, she is seen 
from the earth to the westward of him, and is 



VENUS. 213 

called the morning star ; but when she sets after 
him, she is eastward of him, and is then an even- 
ing star. She is alternately one or the other about 
290 days. 

The following drawing shows the appearance 
of Venus when viewed through a very powerful 
telescope : 




Venus, like Mercury, sometimes passes over the 
sun's disc, but the transits of Venus occur much 
less frequently than those of Mercury ; they have 
this peculiarity, that the spaces of time between 
the five transits are 8 years, 122 years, 8 years, 
and 105 years, and that they can happen only in 
the months of June and December. The first 
observation of a transit of Venus was made by 
Horrox in 1639. The following is a list of all the 
transits of Venus which have occurred or will 
occur, from 1639 to the 22d century. 

1639 Dec. 4. 1882 Dec. 6. 

1761 June 5. 2004 June 7. 

1769 June 3. 2012 June 5. 

1874 Dec. 8. 

15 



214 VENUS. 

The transit of June 5th, 1761, was not very 
successfully observed. That of June 3d, 1769, 
was observed by astronomers with great care in 
every part of the globe. Among the most suc- 
cessful, were those of a committee of the American 
Philosophical Society, at the head of w 7 hom was 
Rittenhouse. The observations of both transits 
have been reduced with great care by Encke, who 
makes the mean horizontal equatorial parallax of 
the sun S".578. 

This computation of Encke is generally recog- 
nised by astronomers as constituting the basis of 
the solar system. The distances of the other 
planets are deduced from it by Kepler's third 
law. 

Venus appears, w r hen on the sun, like the draw- 
ing for Mercury, except that she is larger in pro- 
portion to the size of the sun. 

Her year of230§ solar days is divided, for both hemispheres, 
into seasons of nearly equal length, since the eccentricity of 
its orbit is very small. For the same reason, the days are 
all nearly equal in length ; the intensity of the light received 
from the sun is at all times nearly the same, being 1 ^ that 
at the earth ; and the apparent diameter of the sun's disc va- 
ries only from 44' 32".4 to 43' 56". 1. 

Mercury is the only planet which can, for Venus, make a 
transit over the sun's disc ; these phenomena occur much 
oftener there than at the earth, and this planet appears much 
larger at Venus than at the eartN. The earth is by far the most 
brilliant star in the evening sky of Venus; its brilliancy at 
midnight, at the time of its opposition, is 8 times the maxi- 
mum brightness of Venus as seen from the earth. From no 
othei body of the system, except our moon, does the earth 



THE EARTH. 215 

appear so bright. At Venus our moon outshines Mars, which 
appears less brilliant there than at the earth. Mercury is for 
Venus nearly the same as the latter is for the earth, and it 
presents the same variety of phases. When the earth is in 
quadrature, about f of its disc is illuminated. Observations 
of the eclipses of our moon, and also of her transits over the 
earth's disc, are of great importance at Venus. 

The daily motion of the stars is only a little less rapid than 
for the earth. A pound at the earth weighs 14J ounces at 
Venus. Since the magnitudes and masses of these two bo- 
dies are nearly equal, the velocity of falling bodies will be 
nearly the same for both. 

Mercury and Venus are called inferior planets, 
because their orbits are within that of the earth: 
they are the only planets that produce transits over 
the sun's disc as seen from the earth. 

As a goddess, Venus was extensively worship- 
ped by the heathens, under various names, as 
Ashtaroth, Astarte, Aphrodite, Cotitta, &c. As 
the morning star, she is known by the titles of 
Phosphorus and Lucifer; as the evening star, by 
those of Hesperus and Vesper. Her sign 5 among 
astronomers is said to resemble a mirror with a 
handle at the bottom. 



SEC. 10. 

THE EARTH, 

The next planet in order from the sun, is dis- 
tant from that luminary 95,000,000 of miles. Its 
equatorial diameter is 7935 miles ; its circumfer- 



216 THE EARTH. 

ence upwards of 25,000 miles at the equator; and 
its superficies nearly 199,000,000 of square miles. 
The mass of the earth is 554V3T °f the sun's mass. 
Its density is 4 times that of the sun, and 5§ times 
that of water. 

The figure of the earth is spherical, except that 
it is a little flattened at the poles, where the diame- 
ter is 36 miles shorter than at the equator. The 
true shape of the earth was long a contested point 
among philosophers: some of the ancients, as Leu- 
cippus, Anaximander, &c, supposed that it had 
the figure of a drum ; but the most prevailing 
opinion was, that it consisted of a widely-extended 
plain, of which the visible horizon formed the 
boundary, firmly fixed upon some unknown basis, 
or floating upon an abyss of waters. Of this last 
opinion were not only some of the ancient poets 
and philosophers, but also some of the Christian 
fathers, as Lactantius, St. Augustine, &c. The 
spherical figure of the earth is now, however, ad- 
mitted by ail true philosophers and astronomers; 
it is proved by the form of its shadow upon the 
moon at the time of an eclipse ; by the fact of ships 
sailing round it; and by the tops of distant objects 
being visible, as they are approached at sea, long 
before their bottoms can be seen. The flatness of 
the earth at the poles, and its elevation at the equa- 
tor, have been ascertained by experiments with a 
pendulum, and by measurements on the arc of a 
meridian in different parts of the world. 

The revolution of the earth about its axis begets a centri- 



THE EARTH. 217 

fugal force, which acts in opposition to the force of gravity. 
At the equator, the centrifugal force is -^--^ of the force of gra- 
vity. If the velocity with which the earth revolves about its 
axis w 7 ere just seventeen times as great as it actually is, the 
centrifugal force at the equator would be just equal to the 
force of gravity, and bodies at that place would have no 
weight. 

The compressed form of the earth, and the centrifugal 
force, cause bodies in different latitudes to have different 
weights. A body whose weight at the equator is 1, has at 
the pole a weight of 1.005176. 

A body falls in a vacuum, in the first second of time, at 
the equator, 16.044 feet; and, at the pole, 16.127 feet. 

The length of a seconds pendulum is 3.2510 feet at the 
equator, and at the pole it is 3.2681 feet. From this it will 
be seen that a clock, with a seconds pendulum regulated at 
the equator, if transported to one of the poles would gain 3 
minutes 43 seconds daily. 

The earth has two sensible and two insensible 
motions. The sensible motions are its annual 
revolution round the sun, and its diurnal rotation 
upon its own axis. The annual revolution, which 
forms its year, and by means of the inclination of 
its poles produces the seasons, is performed in an 
orbit of nearly 598,000,000 miles, in about 365J 
days, moving from west to east at the rate of 
68,000 miles an hour, or nearly 20 miles each second. 
The diurnal rotation, which produces alternate 
day and night, is performed upon its own axis 
once in 24 hours; or, to speak more accurately, in 
23 hours 56 minutes 4 seconds: by which, in ad- 
dition to the orbital motion just noticed, the people 
dwelling on the equator are whirled around at the 



218 THE EARTH. 

rate of 1042 miles every hour, and those on the 
parallel of Philadelphia at the rate of 648 miles 
per hour ! 

The insensible motions of the earth arise from 
the precession of the equinoxes, and the decrease 
in the obliquity of the ecliptic; or, what is the 
same thing, the decrease of inclination of the 
earth's axis. The former is 50 T 2 ¥ VV seconds in a 
year; the latter has been estimated at 47 T 6 o sec- 
onds in a century. 

DAY AND NIGHT. 

By the rotation of the earth upon its axis once 
in 24 hours, the alternation of day and night is 
produced. For, as the earth is spherical, it can 
present but one of its sides to the sun, and the 
other side must in the mean time remain in dark- 
ness. A ball, with a wire passing through its 
centre, on which it may turn freely, will afford an 
easy illustration of this, if held before a candle, or 
lamp: and any point marked upon the ball may 
represent any given place of equal latitude upon 
the globe, which the point would occupy upon the 
ball, w 7 ere it divided into northern and southern 
hemispheres, with their appropriate parallels of 
latitude. 

There are certain places on the earth, where 
only one day and one night are known in a whole 
year. These are situated at the poles ; and from 
thence to the polar circles, the days and nights are 
of some months' continuance, according to their 



THE EARTH. 219 

vicinity to, or distance from, the poles. To un- 
derstand this, it is necessary to advert to the 
inclination of the earth's axis, and to keep in mind 
that the sun is always vertical to some one point, 
and only one at the same time, upon the terres- 
trial globe ; from this point its rays reach ninety 
degrees every way, which is the whole extent of 
a hemisphere. When, therefore, the sun is on the 
equator, his rays extend to either pole ; but when 
advanced a certain number of degrees to the north 
of the equator, his rays extend the same number 
of degrees beyond the north pole, but are with- 
drawn in an equal proportion from the south pole. 
When he is vertical to the tropic of Cancer, his 
greatest distance north of the equator, he of course 
shines to the same number of degrees on the other 
side of the north pole — that is, to the arctic circle — 
while the regions of similar latitude in the south 
are left in darkness. While he thus shines over 
the north pole to the arctic circle, no night can be 
experienced there ; and, on the contrary, the re- 
gions on the south, within the antarctic circle, are 
deprived of the benefit of day. Hence it is evident 
that there can be in a year but one day and one 
night at the poles, each half a year in length. 
For, from the moment the sun ascends north of 
the equator, his rays reach over the north pole, 
which he continues to illuminate till he returns to 
the equator ; a period of half a year. 

The reverse of this happens with respect to the 
south pole, while the sun is south of the equator, 



220 THE EARTH. 

till he reaches the tropic of Capricornus. In both 
cases, the parts between the poles and the polar 
circles will have their days and nights prolonged, 
in proportion to the declination of the sun from 
the equator. 

The inhabitants of the polar regions are not, 
however, in total darkness, even when the sun 
does not actually rise upon them; for, in the first 
place, his appearance to them is both anticipated 
and retarded, by the power of refraction, much 
longer than to us : and, in the second place, they 
have a very long twilight, before his rising and 
after his setting; for the twilight begins when 
the sun is within eighteen degrees of the hori- 
zon, and continues till he has sunk to the same 
distance below it ; and his greatest depression 
is but 23i degrees, or 5^ more than will afford 
them twilight. In addition to this, the moon is 
above the horizon of the poles for a fortnight to- 
gether; for, as she passes monthly through the 
whole ecliptic, which is one half north and the 
other half south of the equator, she must continue 
to shine over one or the other of the poles till she 
returns to the equator. The polar regions have also 
a third benefit, in having their winter full moons 
in the highest altitude, describing nearly the same 
track as their summer sun. 

THE SEASONS. 

Upon the position of the earth's axis towards 
the sun, depends not only the length of days and 




The Seasons. 



THE EARTH. 221 

nights, but also the variety of the seasons. By 
the inclination of the axis of the earth, every part 
of the planet is by turns presented to the sun : and 
in those parts where the sun's rays fall most per- 
pendicularly, it is summer; but where they fall in 
the most oblique direction, it is winter. The in- 
termediate periods, between the greatest and least 
obliquity of the sun's rays falling on any place, 
are the seasons of autumn and spring at that 
place. 

In June, the north pole of the earth inclines to 
the sun, and brings all the northern parts into the 
light ; in these parts, therefore, it is summer. In 
December, when the earth is in the opposite part 
of its orbit, the north pole declines from the sun, 
and the south pole approaches it; and then it is 
summer to the parts south of the equator, and 
winter to the north of it. In March and Septem- 
ber, the sun is perpendicular to the equator ; and 
then there is equal day and night at all places, 
except at the poles, which are the boundary of 
light and darkness. At this season, spring and 
autumn prevail north and south of the equator ; 
but under that line it is high summer. 

These changes are illustrated by the diagram, 
in which A represents the situation of the earth 
at the vernal equinox in March, when the spring 
commences, and the light falls on both poles. C 
shows the summer solstice in June, when the 
north pole is turned 23^° towards the sun. B is 
the autumnal equinox in September, when both 



222 THE EARTH. 

poles are again illuminated. D is the winter sol- 
stice in December, when the north pole is again 
in the dark, and the south pole is inclined 23J° to 
the sun. When it is winter in the northern hemi- 
sphere, it is summer in the southern; and vice 
versa. 

THE EARTH'S SATELLITE. 

The earth is attended by a secondary planet, or 
satellite, the moon, which reflects upon certain 
portions of its surface, during the night, the light 
which she receives from the sun ; and in like man- 
ner the earth reflects the light of the sun upon the 
moon during her night. The earth, no doubt, pre- 
sents to the inhabitants of the moon changes 
nearly similar to those which we witness in that 
luminary ; only the earth must appear to them 
more than thirteen times as large. When it is 
new moon to our earth, it is full earth to the moon, 
and vice versa. 

THE ATMOSPHERE. 

The earth is surrounded with a thin fluid sub- 
stance, called the atmosphere, by means of which 
the rays of light are reflected, and equally dis- 
persed in all directions, Hence the heavens ap- 
pear bright in the day-time; for, without this 
atmosphere, only that portion would be illumina- 
ted in which the sun shines; the rest would ap- 
pear as dark as the night, and the stars would be 



THE EARTH. 223 

seen; neither would there be any twilight, but a 
sudden transition from sunshine to the blackest 
darkness at sunset, and from darkness to the blaze 
of a partial day at sunrise. This atmosphere also 
constitutes the air we breathe, without which we 
could not exist ; and in it are produced the va- 
rious phenomena of thunder, lightning, wind, rain, 
snow, meteors, &c. 

This atmosphere is most dense at the surface 
of the earth, and increases in rarefaction as it 
rises, till it becomes unfit to support human life. 
Its precise height is not known, but, by calcula- 
tion, it is found sufficiently dense at the height of 
4<4 miles to reflect the rays of the sun, and hence 
to produce twilight. Its weight is immense; for 
the quantity that presses on a person of moderate 
size is calculated at 32,400 lbs. avoirdupoise, or 
nearly 14^ tons ; a weight sufficient to crush him 
to atoms, were it not counterbalanced by the 
molecular repulsion of the particles of the body, 
and those of the air which is diffused through 
most parts of the human frame ; so that no incon- 
venience is sustained. 

The mass of the atmosphere is a little less than a millionth 
part of the earth's mass. If the atmosphere had the same 
density throughout which it has at the earth's surface, its 
height would be, in round numbers, 261,000 feet. But, since 
the density diminishes as the height above the surface of the 
earth increases, the height of the atmosphere is of course 
greater than that. It cannot possibly have a height exceed- 
ing five times the earth's radius ; for at that height the cen- 
trifugal force is equal to the force of gravity, and it would 



224 THE EARTH. 

consequently be separated from the upper part of the earth's 
atmosphere, and scattered through space On that account, 
we presume that it does not reach that height ; but that, by 
the extreme cold there, it is hindered from any further expan- 
sion, and is changed into liquid. For every 300 feet of rise 
above the surface of the earth, the heat of the atmosphere 
diminishes 1° of Fahrenheit 

The atmosphere, like other transparent media, refracts the 
rays of light which pass obliquely through it; and, owing to 
its variable density, these rays of light describe a curved 
line, with the concavity toward the earth. For this reason, 
all the heavenly bodies appear to be higher than they really 
are, unless when placed exactly at the zenith. 

The state of the barometer being 29' 5".9 British inches, 
and the temperature 48°. 9 Fahrenheit, the refraction in the 
horizon amounts to 36' 7", and at the altitude of 45° to only 
57''.5 ; in the zenith it is always nothing. 

When the atmosphere is thrown into motion, it 
constitutes wind, which is warm, cold, or moist, 
according to the temperature of the climates 
where it is generated ; producing heat, frost, or 
rain, as it is more or less imbued with those prin- 
ciples. In the atmosphere, also, the vapours which 
constantly arise from the earth are condensed, and 
become clouds ; and these, w 7 hen they exceed in 
weight that of the atmosphere, fall in showers. 

The earth is composed of land and water, the 
description of which belongs to geography : suf- 
fice it here to observe, that the water, besides its 
currents, is subject to a diurnal motion, called a 
tide, occasioned by the attractive powers of the 
sun and moon. 

The most certain investigations teach us that 



THE EARTH. 225 

the earth's axis is immovable, with reference to 
the earth itself, and that the equator and the poles 
always occupy the same position upon its surface. 
But the position of the axis in space is constantly 
changing ; in a period of 25,600 years, the north 
pole describes a circle about a certain mean place 
of the pole of the ecliptic. The following list of 
north polar stars will serve to give an idea of the 
nature of this motion. 

B.C. 4000, i Draconis, 3d magnitude, 4° from the pole. 

" 1700, a Draconis, 2d " very near. 

A.D. 2150, a Ursse Min., 2d " 20' from " 

" 4200, y Cephei, 3d " 1° 50' " " 

" 6000, £ Cephei, 3d " 4° " " 

A.D. 7500, a Cephei, 3d magnitude, 2° from the pole. 

" 10,200, a Cygni, 1st " 7° " " 

" 11,400, 6 Cygni, 3d 3° " " 

" 13,800, a Lyrae, 1st " 5° " " 

From this time, a period of 7800 years elapses, 
during which only stars of the 4th and inferior 
magnitudes are near the pole ; and then, A. D. 
21600 the star i Draconis again occupies the same 
position with respect to the pole that it did 4000 
years B. C. 

Our present pole star has held that rank since 
the time of Hipparchus, and will continue to hold 
it till the year 3200. 

The southern polar stars have been, in former 
times, among the brightest stars in the Ship Argo. 
At present there is no star brighter than those of 
the 5th or 6th magnitude near the south pole. 



226 THE EARTH. 



2000 years hence, the star (3 of the Little Water- 
Serpent will supply this deficiency. After that 
time this pole passes through a portion of the 
heavens in which there are no bright stars. The 
brilliant star Canopus will be within 8° of the 
south pole when Vega or a Lyrse forms our north 
polar star. 

This change in the position of the axis of the 
heavens is attended with the consequence that 
many constellations now invisible in the United 
States will become visible, and vice versa. For 
example, the constellations of the Crane, the In- 
dian, the Peacock, the Bird of Paradise, the South- 
ern Triangle, and some others, which are at pre- 
sent invisible in the latitude of Philadelphia, will, 
12000 years hence, rise above the horizon of that 
place. And, on the other hand, the Great Dog, 
the Hare, the Dove, and the northern part of the 
Ship Argo, which are now visible here, will then 
have entirely disappeared from our view. 

At that time, also, the equator of the heavens 
will occupy a place among the stars very different 
from its present position. The vernal will then 
be very near where the autumnal equinox is now; 
and the equator will pass through the Band of the 
Fishes, the Northern Fish, the Smaller Triangle, 
the Head of Medusa, Perseus, the Charioteer 
(very near Capella and )3 in this constellation)., 
the Lynx, the Great Lion, the Virgin, the Hydra, 
the Wolf, the Scorpion, the Altar, the Southern 
Crown, the Southern Fish, and the Water-Bearer. 






THE EARTH. 227 

A second variation is that which the disturbing influence of 
the planets causes in the position of the earth? s orbit; the 
effect of which, after a very long period, will be a slight 
change in the seasons and in the length of the days. This 
variation is not sufficient to produce any sensible change in 
the climate at different periods; and we must look to other 
than astronomical causes to account for the fact that tropical 
plants and animals have been found in higher latitudes. 

Definition. — The general statement of the law 
of gravity for the system (see page 198), supposes 
all the bodies combined to constitute one central 
body. This is never the case in reality. The 
separate bodies are continually changing their 
places with reference to that centre ; hence arises 
a variation of the attraction referred to the centre 
of the system. This is called the perturbation, or 
disturbance, of the motion of the planet or satel- . 
lite. It is usually very small, compared with the 
principal force* 

A third variation is that which takes place in the position 
of the perihelion of the earth's orbit. The earth is nearest the 
sun 10 days after the winter solstice of the northern hemi- 
sphere ; 58 years hence this will happen one day later ; and 
after a period of 10,000 years has elapsed, it will be in its 
perihelion on the longest day of summer. This will exercise 
some influence upon the duration of the seasons. At the 
present time, in the northern hemisphere, the winter is 89, the 
spring is 92J, the summer 93J, and the autumn is 90 days 
in length; 10,000 years hence the winter will contain 93 J, 
the spring 89, the summer 89, and the autumn 93 J days. 
The intensity of the summer heat will, be only slightly in- 
creased, and that of the winter cold will be a very little 
greater than at present. If the eccentricity of the earth's 
orbit were as great as that of the orbit of Mars or Mercury, 



228 SECONDARIES, MOONS, OR SATELLITES. 

such a change in the place of the perihelion would produce a 
far greater variation both in the lengths of the seasons and in 
the intensity of the heat and cold. The eccentricity is about 
^o of the semi-diameter of the earth's orbit, and it is subject 
to a very slight variation only, so that the inhabitants of the 
earth would probably never remark these changes, if it were 
not for the investigations of astronomers. 

The earth was deified among the heathen idola- 
ters, under the various titles of Ge, Terra, Tellus, 
Cybele, Rhea, Vesta, Ceres, Bona Dea, Thea, 
Titaea, &c., and was called the wife of Caelus, or 
Uranus, and the mother of the Titans, the Giants, 
the Cyclops, &c. She was represented as crowned 
with turrets, holding a sceptre in one hand and a* 
key in the other, with a tame lion lying at her 
feet. 

The astronomical sign of the earth © represents 
the terrestrial globe, with the equator. Some- 
times it is indicated by a globe, surmounted with 
a cross, thus 6. 



SEC. 11. 

GENERAL REMARKS CONCERNING SECONDARIES, MOONS, 
OR SATELLITES. 

The proximity of the Moon to our earth, about 
which, as a centre, it revolves, enables us per- 
fectly to explain most of the circumstances attend- 
ing it. But a knowledge of the duration of the 
seasons, the length of the day. &c, is of little in- 
terest to us compared with that of the character 



PLANETS, MOONS, OR SATELLITES. 229 

of its surface and other highly important *acts 
relating to its position in the universe. We 
know the existence of rugged mountains, their 
forms and heights, and also the absence of a re- 
fracting and light-absorbing envelope or atmo- 
sphere. This fact being firmly established, ena- 
bles us to delineate the surface of the moon with 
precision. 

Some general features of this kind may be sup- 
posed to be common to all the satellites of our 
system : others, on the contrary, depend upon 
some peculiarities, and are, therefore, more or less 
different for each individual. They have much 
in common with their primaries: the apparent 
magnitudes of the sun, planets and comets ; their 
places in the heavens, with reference to the fixed 
stars and to each other; the intensity of the sun's 
light, and the length of the year, are very nearly 
the same for a planet and its satellites ; the eclipses 
are of an opposite character; the conjunctions, 
oppositions, transits, of the inferior planets — in 
short, all the phenomena which depend merely 
upon the position of the body in space — will be 
of the same character for the whole system of a 
planet, as for the primary. 

It is ascertained with certainty for our moon, 
the four satellites of Jupiter, and the most distant 
one of Saturn — and with a high degree of proba- 
bility for all the other satellites of the solar sys- 
tem — that the times of rotation about their axes 
are equal to the periods of revolution about their 
16 



230 PLANETS, MOONS, OR SATELLITES. 

primaries. Hence it follows that the length of 
their days will be equal to their synodic periods 
of revolution; and, consequently, they are, with- 
out exception, much longer than the days of the 
primary planets; an extraordinary advantage 
possessed by the satellites, in regard to accurate 
investigations of the heavenly bodies; for the 
slowness of the apparent motion permits not only 
a long-continued, but especially a peaceful and 
undisturbed, observation of them. 

Another consequence of the equality of their 
periods of revolution and rotation is, that their 
primaries do not partake of the apparent daily 
motion of the other heavenly bodies ; but, for each 
given place on the surface of a satellite, the planet 
occupies a constant mean place in the heavens 
with reference to the horizon and the meridian. 
It fluctuates about this mean place within certain 
limits, whose distance depends upon the inequality 
of the moon's motion, called libration ; the alter- 
nate rising and setting of the whole, or a portion, 
of the primary planet can occur only to a very 
small portion of the satellite — to by far the greater 
part of the latter, the former is either always visi- 
ble or always invisible. 

The primary planet is by far the largest body 
in the firmament, for all its moons; and appears, 
as seen from each, many times greater than any 
of the other satellites. All parts of the planet 
(with the exception, in some instances, of the polar 
regions) are visible in succession at its moon; 



PLANETS, MOONS, OR SATELLITES. 231 

whilst the inhabitants of the former never see but 
one side of the moon, and can therefore know no- 
thing directly concerning the other side. This is 
another great advantage possessed by the satellites 
over their primaries. 

Finally, each primary, as observed from either 
of its satellites, will present the same variety of 
phases that our moon does to us. The period of 
these phases is no other than the lunar day, since 
both are equal to that of the synodic revolution. 
To that part of the moon in the meridian of which 
the primary is situated, one-half of the disc will 
appear illuminated each evening at sunset, or it 
w 7 ill be in its first quarter ; at each midnight it 
will be in opposition, and will present its full en- 
lightened disc towards the moon; each morning 
at sunrise it will be in its last quarter ; and at 
mid-day it will be in conjunction and entirely 
invisible, corresponding with our new moon. 
Eclipses of the sun occur for each satellite much 
oftener, and are larger and of longer duration, 
than for its primary ; and, on the other hand, the 
eclipses of the latter are, for the satellite, merely 
the passages of its own very small shadow over 
the disc of the planet. 

These are the essential features common to all 
the satellites, which lead us to the conclusion that 
they are far better adapted for observations of the 
heavens, than are the primary planets. The lat- 
ter, on the contrary, possess, in some respects, 
advantages over the former : the determination of 



232 THE MOON. 

the orbit of a heavenly body, from observations 
made at one of the primaries, presents fewer theo- 
retical difficulties than if the body were observed 
from a secondary planet ; for, to the difficulty for- 
merly alluded to, occasioned by the motion of the 
planet about the sun, is added that of the motion 
of the satellite about its primary. 

The force of gravity upon the moons of the solar 
system is much less than upon the primary pla- 
nets : the greatest distance through which a body 
falls during the first second, at any of the former, 
is about three feet ; and at some of the satellites 
it is less than one foot ; whilst at the planets, (the 
asteroids excepted), the least distance passed 
through by a falling body during the first second 
is eight feet. 

The ratio of the forces of gravity is the most 
important element for the motions of all bodies; 
for it determines the measure of the force required 
to produce such motions. In the case of the sun, 
the earth and her moon, this ratio is expressed by 
the numbers 185, 6J and 1. 



SEC. 12. 

J) THE MOON. 

Our moon belongs to the class of secondaries, 
or satellites. She receives, like the primary pla- 
nets, her light and heat from the sun. In common 
with her primary, the earth, she revolves round 



THE MOON. 233 

the sun in a year. She also revolves around the 
earth, in an elliptical orbit, at the rate of 2290 
miles in an hour, at a mean distance of 238,000 
miles. Such is the orbital velocity which the joint 
masses of the earth and moon, or tellurian system, 
is capable of impressing upon a body at that dis- 
tance. She completes her revolution round the 
earth in 29 days 12 hours 44 minutes, nearly. 
This time of the moon's revolution is called a 
synodical month ; but, in consequence of her con- 
joint motion with the earth around the sun, she 
appears to revolve from one point in the heavens 
to the same point again, in about 27 days 7 hours 
43 minutes, which constitutes a siderial or peri- 
odical month. 

Her diameter is about 2159 miles, and her bulk 
about a fiftieth part of that of the earth. Her ap- 
parent motion is that of rising in the east and set- 
ting in the west ; but this is owing to the revolu- 
tion of the earth upon its axis. The moon's real 
motion round the earth is from west to east. This 
may be ascertained by remarking, when she is 
near any particular star, she will approach it 
from west to east, then be in conjunction with it, 
and ultimately pass eastward of it. 

The moon accompanies the earth in its annual 
orbit round the sun, and revolves upon her own 
axis towards the west in the same time that she 
goes round the earth ; so that she always presents 
the same face to us, with only a slight variation, 
caused by her librations. Hence, in every revo- 



234 THE MOON. 

lution, a small portion of her face is carried out 
of sight on one side, and an equal portion is 
brought forward on the other. This irregularity, 
which arises from the moon moving about the 
earth towards the east, while her rotation upon 
her axis is towards the west, amounts to about 1\ 
degrees on each side, and is called her libration in 
longitude. And, in consequence of the moon's 
axis being inclined to the plane of her orbit, some- 
times one of her poles is inclined towards the earth, 
and sometimes the other; so that we occasionally 
see more or less of her northern and southern polar 
regions : this is called her libration in latitude, and 
amounts to about 5^ degrees at each pole. 

From the simultaneous motion of the moon upon 
her axis and in her orbit, it is evident that she can 
have but one day and one night in one of our lu- 
nar months ; and as she encompasses the earth 
not quite thirteen times during his progress round 
the sun, it is equally manifest that her year is 
somewhat less than thirteen of her days. And as 
her axis is almost perpendicular to the plane of 
the ecliptic, she can have little diversity of sea- 
sons, or of length of days. 

The earth, as already remarked, reflects the 
sun's rays upon the moon, in the same manner 
that the moon reflects them to the earth; but, in 
consequence of the coincidence of motion between 
the two bodies, only one half of the moon ever 
receives the reflection of the earth, and that half 
is of course never in total darkness ; for, when 




Phases of the Moon. 



THE MOON. 235 

turned from the sun, it is illuminated by light re- 
flected from the earth, in the same manner as we 
are enlightened by a full moon ; but the other 
hemisphere of the moon has a fortnight's light and 
a fortnight's darkness, alternately. Hence the 
inhabitants (if any) of one half of the moon never 
see the earth, unless they travel to gratify their 
curiosity ; for which purpose those on the meri- 
dian, opposite to the middle of the enlightened 
disc, would have to go more than 1700 miles; but 
their trouble would be more than compensated by 
the sight of an illumined body thirteen times the 
size of their own globe, and which would appear 
to them the largest body in the universe. 

The sun and stars rise and set, to the inhabit- 
ants of the moon, in the same manner as they do 
to us. 

PHASES OF THE MOOtf. 

The moon being, like the other planets, a dark 
or opaque body, enlightened by the sun, can only 
be illuminated on one of her sides at a time ; and 
hence the different appearances, or phases, which 
she presents to our view : for, as the light of the 
moon, visible on the earth, is on that part of her 
body which is turned towards us, we perceive, 
according to her various positions with regard to 
the sun and earth, different degrees of illumina- 
tion. (See the drawing.) Thus she appears at 
first horned, (in the west, just after sunset,) and 



236 THE MOON. 

continues to increase in size till she attains a half 
circle, and ultimately a complete one. She then 
begins to wane ; that part which we first saw is 
withdrawn from our sight; she presents a half 
circle on the contrary side to that in which it 
was before observed ; this decreases to a horned 
streak, and then she disappears. 

The disappearance of the moon takes place 
when she comes to a conjunction with the sun; 
that is, when she is between that luminary and 
the earth; because her unenlightened side is then 
towards us : this is called the change, or new 
moon. When she is in opposition to the sun — 
that is, when she has proceeded through half her 
orbit — she presents her whole illuminated side to 
the earth, and is then called a full moon : at both 
these seasons, she is said to be in her syzygies. 
When in her quadratures, or a quarter of a circle 
from the sun, she appears half full, because only 
one half of her enlightened side is toward the 
earth ; at these times the moon is said to be in her 
first or last quarter, according as she is advancing 
from or towards her change. Before and after 
her quadrature, she has all the possible variety of 
phases between a thin circular line and a full 
face. (See the drawing of the moon's phases.) 

When the sun and moon are in opposite parts 
of the heavens — that is, at the time of full moon — 
the latter rises in the east, as the sun sets in the 
w r est. From the change to the full moon, the illu- 
minated part is towards the west, because the sun 



THE MOON. 237 

is then westward of it ; but, from the full moon to 
the change, the illuminated part is turned to the 
east, the sun being then eastward of it. 

When the moon, at the time of her change, passes 
in a right line between the sun and the earth, her 
shadow is projected upon the latter, and obscures 
the light of the sun, which is called an eclipse of 
that luminary ; and when, at the time of full moon, 
the earth interposes between the sun and the 
moon in a right line, the shadow of the earth is pro- 
jected upon the moon, and a lunar eclipse is the 
consequence. It is therefore only in conjunctions 
of the sun and moon that solar eclipses can occur ; 
and lunar eclipses can only happen at the time of 
their opposition, and then only when the planets 
are in the same plane, or nearly so. Owing to 
the inclination of the moon's orbit to that of the 
earth, eclipses do not take place at every change 
and full of the moon : there may be as many as 
seven, but seldom more than six, eclipses in one 
year; and very frequently not more than two of 
each luminary. 

The inclination of the ecliptic to the equator 
occasions a peculiar phenomenon of the moon, 
called the harvest moon. This occurs in Septem- 
ber, when the moon for several successive even- 
ings rises about the same time, soon after sunset. 
This is owing to the peculiar ascent of the eclip- 
tic, as may be discovered by turning a celestial 
globe, when some signs will be seen to ascend 
rapidly and obliquely, others slowly and almost 



238 THE MOON. 

perpendicularly : when the full moon is in the 
former, it deviates from its custom of rising each 
evening about forty-nine minutes later than on the 
preceding; and as this variation takes place about 
the time of harvest, and is of considerable use in 
lengthening out the day, it is called the harvest 
moon. 

The full moon, seen through a telescope of 
moderately magnifying power, presents a very 
beautiful sight, diversified with great variety of 
lustre and colour; but the mountains are best 
observed at the time of her increase and de- 
crease. 

In consequence of the absence of an atmosphere 
surrounding our moon, the heavens by day must 
appear there much darker than upon our highest 
mountains : there, dazzling light and nightly 
shades immediately succeed each other without 
the agreeable intervention of a twilight ; and the 
occasional cloudy and obscure days, which upon 
the earth have an influence so salutary, are en- 
tirely unknown at the moon. Perhaps even the 
brighter stars are there visible in the day time. 
The hemisphere towards the earth is illuminated 
by it fourteen times as brilliantly as our night is 
by the moon : hence, the view of the other hea- 
venly bodies by night must be much more splen- 
did from the other side than from this. For there, 
nothing interrupts the perfect serenity and dark- 
ness of the night. The 350 hours of one of these 
clear nights, is a number greater than the nights of 



THE MOON. 239 

a whole year usually afford for observations of the 
heavenly bodies upon the earth's surface. 

The above remarks apply only to f of the moon's surface at 
which the earth is never visible, at the opposite parts of the 
same dimensions it is always visible, and at the intermediate 
seventh part the earth is alternately above and below the 
horizon. The latter portion is a zone of unequal width 
through the poles of the moon; its width at the poles is 255, 
at the equator 292, and at the parallels of 40° N. and S. 394 
miles wide ; and the middle of this zone is the mean border 
which the moon presents to us. 

The sun appears, when seen from the moon, of about the 
same size as when seen from the earth ; its apparent diameter 
varies from 32' 39".5 to 31' 25".3. The earth, as seen from 
the moon, varies in apparent diameter from 1° 47' 48".l to 
2° 2' 58".8, or nearly 4 times the diameter of the moon as it 
appears to us. 

The difference between the longest and shortest days is 
much less for the moon than for the earth, owing to the small 
inclination of the moon's equator to the plane of her orbit. 
At the pole the length of the day is 179 of our days. The 
sun there can never be more than 1 J° above or below the 
horizon; and since a person, at the pole of the moon, has but 
to elevate himself 2000 feet above the surface to be able to 
see I|° below the horizon, he may by so doing attain perpe- 
tual sunshine. There are peaks of mountains far higher than 
this, in great numbers, in the neighbourhood of both poles. 
Into many of the valleys and plains in these regions, the sun 
never shines ; and the only light they enjoy the benefit of, is 
that w T hich is reflected by the surrounding mountains, which 
constitutes for them a kind of twilight, similar to that which 
is enjoyed by the inhabitants of the deep valleys of Norway. 

The lunar year is the same as ours ; the difference of sea- 
sons is so small as scarcely to be perceptible, for the height 
of the sun only varies 3° from summer to winter. 



240 



THE MOON. 



As at the earth we have eclipses of the sun 
and moon, so at the moon there will be eclipses 
of the sun and earth, from a similar cause; and, 
for the most part, at the same times, but generally 
of an opposite kind. The following parallel may 
be drawn between the eclipses which occur at 
corresponding times at the earth and at the moon: 



At the Earth. At the Moon. 


A total eclipse of the moon. 


A total eclipse of the sun for 
the whole moon. 


A partial eclipse of the 
moon. 


A total eclipse of the sun for 
a part of the moon ; and 
partial for the remainder. 


Passage of the penumbra 
of the earth over the disc 
of the moon. 


A partial eclipse of the sun. 


A total eclipse of the sun. 


A very small scarcely visible 
eclipse of the earth. 


An annular or partial eclipse 
of the sun. 


Nothing. 



From the above it will be seen that for all our 
lunar eclipses, whether total or partial, a total 
eclipse of the sun is experienced by all or a part 
of the surface of the moon. And, on the other 
hand, that there is no such thing as an eclipse of 
the earth of any importance ; scarcely a 3000th 
part of the earth's surface can ever be covered by 
the moon's shadow at any one time. 

Besides the eclipses of the sun, the fixed stars 
and planets occupying a zone of about 14° width, 
will frequently be occulted by the earth. The 



THE MOON. 241 

greatest duration of an occultation there is 4 
hours; with us it is only about 70 minutes. 

The earth constitutes a timepiece for the moon. 
The four principal divisions of the day are marked 
by the phases of the earth; and since it revolves 
about its axis 29^ times during a lunar day, the 
positions of remarkable mountains, seas or islands, 
upon the disc of the earth, might serve to indicate 
much smaller divisions of time. 

DESCRIPTION OF THE SURFACE OF THE MOON. 

The mountains of the moon differ from those on 
the earth in many respects. Occasionally we see 
high insulated mountains, or peaks, casting a long, 
well-defined shadow on the surface of the moon, 
which affords us the means of a perfect measure- 
ment of their heights. The surface is more vol- 
canic, and the mountains are higher, and the val- 
leys deeper, in proportion to its size, than on the 
earth. Some of the mountains are five miles high, 
and some of the valleys four miles deep. 

There are also extensive mountain ranges on 
the surface of the moon, resembling our Alps, Ap- 
ennines and Andes. Some of these ranges are 
four miles high; some of them run in a straight 
line from north-east to south-west, as the range 
called the Apennines. Others are curved. 

Circular ranges of mountains form a peculiar 
feature of the moon's surface, which has no coun- 
terpart on that of the other planets. These cir- 
cular ridges of mountains resemble a prodigious 



242 THE MOON. 

rampart, or wall, surrounding an extensive plain, 
or valley, sometimes forty or fifty miles in circum- 
ference. These plains are sometimes on a level 
with the moon's surface, and are called walled 
plains ; sometimes depressed a mile or two below 
that level. Sometimes several circular valleys 
are formed within one of these large enclosures, or 
principal valleys. 

The name of Newton has been given by Msedler 
to a lunar cavern, or depression, surrounded by a 
circular range of mountains. This is the deepest 
cavern in the moon. It has several central and 
parallel chains of mountains, and one peak, rising 
a little above the moon's surface, whose height 
above the bottom of the cavern is four and a half 
miles; being the highest mountain, from its base, 
on the whole surface. It is supposed that there 
is no single mountain, on the earth, high enough, 
above its immediate base, to fill this enormous 
cavity. The name of the great philosopher who 
penetrated deepest into the hidden laws of nature, 
has been very appropriately given to this cavern, 
or pit, which is the deepest depression known in 
the earth or moon. 

There are also numerous crater-formed eleva- 
tions, resembling in shape the cup of an acorn 
These appearances are very similar to the volca- 
noes on the earth, except that the bottom of the 
crater is often below the surface of the moon. 
Around many of these extinct volcanoes, there is 



THE MOON. 243 

an appearance of portions of lava thrown out at 
different times, in strata overlapping each other. 

There is good reason for believing that the vol- 
canic force of the moon has been for ages extinct. 
Sir William Herschel's authority has often been 
quoted in proof of the existence of active volca- 
noes. The appearances which he noticed still 
present themselves almost every lunation ; but 
they are attributed by astronomers, to optical ra- 
ther than physical causes. The remarks of Her- 
schel are considered rather as descriptive of the 
appearances, than as an affirmation of the exist- 
ence of active volcanoes. 

Some have supposed that the cause of the pre- 
sent inactivity of the lunar volcanoes, is to be 
found in the smallness of the moon's size, and the 
want of an atmosphere, in consequence of which 
the process of radiation has reduced the tempera- 
ture of its crust too low for this force to prevail. 

The central mountains are situated in the mid- 
dle of the circular plains. They are usually found 
precisely in the centre ; they rise to the height of 
one or two miles, and cast a well-marked shadow 
on the plains below. Sometimes these central 
mountains terminate in several small distinct 
peaks. 

The crater -formed elevations reflect more light 
than any other portion of the moon, and hence the 
ranges of these elevations form at the time of full 
moon a number of streaks or radiations. These 
appear to meet in a large bright spot, surrounded 



244 



THE MOON. 



by a faint shade called Tycho. Maps of the 
moon's surface have been made which contain the 
names of several conspicuous objects on the moon's 
surface, to which the appellation of seas, lakes, 
gulfs, &c, has been given, rather from a fancied 
resemblance to such objects, than as indicative of 
their real existence. The names of distinguished 
philosophers and astronomers have also been as- 
signed to many of these objects. 

The heights of some of the principal mountains, 
according to the recent measures of Maedler, are 
as follow : 

Posidonius . . 19,830 feet. 

Tycho ... 20,190 

Calippus . . . 20,390 

Casatus . . . 22,810 

Newton . . . 23,830 

Clavius . . . 19,030 

Huygens . . . 18,670 

Blancanus . . 18,010 

Clavius . . . 18,320 

Moretus . . . 18,440 

The worship of the moon formed an important 
part of the ancient heathen rites; and she w r as 
personified under a vast, variety of names ; as Isis, 
Astarte, Selene, Luna, Diana, Proserpina, Hecate, 
Cynthia, Phoebe, and numerous others. The as- 
tronomical sign of the moon is a crescent, 2), or 
the moon in her first quarter. 



3.76 


miles 


3.83 


t< 


3.86 


a 


4.32 


a 


4.52 


66 


3.60 


66 


3.54 


U 


3.41 


St 


3.47 


a 


3.49 


66 



MARS. 245 



SEC. 13. 

C? MARS, 

Whose orbit is next beyond that of the earth, is 
the first of the superior planets, and is known in 
the heavens by its red, dusky appearance: the 
latter proceeds either from a very dense atmo- 
sphere, or from the matter of the planet being best 
adapted for reflecting red rays of light. 

The distance of Mars from the sun is somewhat 
more than 145,000,000 of miles, or half as far 
again as that of our earth ; and, moving at the 
rate of about 55,000 miles every hour, he performs 
his annual circuit, from west to east, in about 687 
of our days. The diameter of Mars is only about 
4135 miles, or a little more than half that of the 
earth. His form is spheroidal, his polar and equa- 
torial diameters being as 15 to 16. When in op- 
position to the sun, he appears about five times as 
large as at the time of conjunction; because, in 
the former case he is much nearer the earth than 
in the latter. It has been supposed that, on ac- 
count of his distance from the sun, Mars cannot 
enjoy more than half the light and heat that the 
earth receives. 

Viewed through a telescope, Mars generally ap- 
pears full ; yet at times he is observed to increase 
and decrease like the moon, but is never horned. 
The plane of his orbit is inclined to the ecliptic 1° 
51' 4"; and his axis is inclined to the former 61° 18'. 
17 



246 MARS. 

He has no satellite. His greatest apparent diame* 
ter is 23", his least 3". 3. The mean value is 5 ".8. 
His volume is 0.140, and his density 0.948, com- 
pared with those of the earth. His mass is 
2,6 8 0,337 that of the sun. A pound here would 
weigh half a pound at Mars. All other circum- 
stances being the same, the amount of light and 
heat at the planet Mars are 0.43 as great as at 
the earth. 

Mars is distinguished from the other planets by 
its reddish light. Spots have been observed which 
do not change their places on the body of the planet. 
The cause of these spots cannot therefore be found 
in an atmosphere surrounding the planet, but must 
be sought for in the difference of the reflection of 
the sun's light by differently constituted portions 
of the surface of the planet, in the same manner 
as upon the earth the green plains, the mountains 
covered with woods, the sandy deserts, the snowy 
fields, &c, all reflect the sun's light differently. 

The spots upon the surface of Mars sometimes 
change their colour a little, from which we may 
infer the existence of an atmosphere. The most 
remarkable of these spots is at the south pole. It 
is large, bright, white, circular and well defined, 
the south pole of the planet being at its centre. 
The magnitude of this spot is changeable, being 
smallest when it is summer, and largest when it 
is winter, in the southern hemisphere of the planet. 
For which reason this spot has been called the 
snowy zone of Mars. (See the drawing.) 



MARS. 247 

The observations of these spots have indicated 
a period of revolution around its axis in 24h. 37m. 
20s., and an inclination of its axis to the ecliptic 
of 63° 9'. 

In its geocentric course, Mars, as well as all the other supe- 
rior planets, can attain every possible elongation from the 
sun. Since its distance from the sun, as is the case with all 
the other superior planets, is greater than the distance of the 
earth from the sun, there will be no inferior conjunction for 
this planet. During the opposition, its retrograde geocentric 
motion is at its maximum. 

Mars moves in the retrograde direction through an arc 
which varies from 11° 8' to 19° 30', in a time varying from 
62 days to 81 days. The elongation from the sun at w T hich 
this retrogradation begins and terminates, varies from 129° 2' 
to 145° 37'. 

The annual period of this planet, occupying 
668§ martial days, is divided into four seasons, as 
follows : 

Northern Hemisphere. Southern Hemisphere. 



Spring 


Autumn . . 


. 1911 days, 


Summer 


Winter . . 


. 181 


Autumn 


Spring . . 


. 149i « 


Winter 


Summer . . 


.147 " 



This very great inequality in the length of the seasons, is 
occasioned by the eccentricity of the orbit of Mars, which is 
more than 8 times as great as that of the earth's orbit, or 
about oy of the diameter. The intensity of the solar light 
and heat in the northern summer is to that in the southern as 
20 is to 29. Hence, it follows, that for the northern hemi- 
sphere the summer is longer with less intense heat, and the 
winter shorter and more mild than for the southern hemi- 
sphere. The surface of Mars may be divided into zones in 



249 MARS. 

the same manner as the earth's, the torrid zone extending 28° 
42' on each side of the equator; the temperate zones, from 28° 
42' to 61° 18' of latitude ; and the frigid zones, from the paral* 
lels of 61° 18' to the poles. The torrid zone, or that portion 
over which the sun will sometimes be in the zenith, occupies 
nearly half the surface of the planet. The inequality of the 
days as well as of the seasons, is much greater for Mars than 
for the earth. The average, or mean length of the day, is 
12h. 19m. 47s. 

Lonarest Day. Shortest Day. 

In latitude 40° 16h. Urn. 8h. 25im? 

" 50 17 54 6 45J 

" 60 22 10J 2 29 

In latitude 42J°, the longest day is double; in 52°, it is 
three times, and in 57 J°, it is 5 times the shortest day. This 
inequality is occasioned chiefly by the inclination of the equa- 
tor to the orbit, but the eccentricity of the latter is another 
source of variation in the length of the day. 

The orbits of Mercury, Venus, the Earth, and the Moon, 
being within that of Mars, there will occasionally be transits 
of these bodies over the sun's disc, as seen from Mars. The 
superior planets adorn the heavens for Mars nearly in the 
same manner as they do for us, but it is less favourably situ- 
ated with reference to the inferior planets. The earth is to 
it what Venus is to us, though only about half as bright; yet 
it is generally the brightest star in its firmament. Both Mer- 
cury and Venus, when seen from Mars, must be very near 
the sun. 

If we consider the intensity of the sun's light at the earth 
equal to 100, it will be at Mars equal to 52 in the perihelion 
and 37 in the aphelion. The apparent diameter of the sun, 
as seen from Mars, varies from 23' 9".4 to 19' 12". 6; or, in 
other words, it appears at that planet about two-thirds as 
large as it does to us. 

The apparent motion of the fixed stars is a little slower 
there than at the earth. The north pole is directed towards 



VESTA. 249 

a point in the Great Bear, which may be found by drawing 
a line from rj of that constellation to a of the Dragon, and to 
this line drawing a perpendicular from £ of the Great Bear; 
the point where these lines intersect, is the north pole of the 
heavens for Mars ; the south pole is very near a of Eridanus 
or Achemar, a star of the first magnitude. 

Mars, among the mythologists, was considered 
as the god of war and of hunting: he bore the 
names of Ares, Arius, Arioch, Mamers, Camulus, 
Woden, Gradivus, Mavors, Quirinus, Enyalus, 
Salisubsalus, &c. The original Mars, to whom 
is ascribed the invention of arms, and the art of 
ranging troops in order of battle, is by many sup- 
posed to have been Nimrod, the Belus of the 
Babylonians, who is mentioned in scripture as " a 
mighty hunter before the Lord :" but this is very 
doubtful. Mars was the reputed son of Juno, and 
is generally represented on antique monuments 
and medals as a robust man, armed with a helmet, 
pike, and shield. Sometimes he is mounted on a 
war-chariot, which is guided by Bellona, the god- 
dess of war, and drawn by two horses, named 
Terror and Fear. Among astronomers, Mars is 
characterised by a spear and shield, J. 



SEC. 14. 

g VESTA. 

Vesta was discovered by Dr. Olbers, a physi- 
cian of Bremen, in the kingdom of Hanover, on 
the 29th March, 1807. It is so very small as to 



250 juno. 

be invisible to the naked eye : through a telescope 
it appears as a star of the 6th magnitude, and of 
a dusky colour. The diameter of Vesta is esti- 
mated at only 238 miles, or, according to some, 
270 miles; her distance from the sun is nearly 
225,000,000 of miles, or 21 times that of the 
earth ; and she performs her annual revolution in 
1325 days. The inclination of her orbit to the 
plane of the ecliptic is 7° 8'. Although the 
mean distance of this planet from the sun is less 
by some millions of miles than that of Juno, or 
Pallas, she is sometimes at a much greater dis- 
tance than either of them, on account of the ec- 
centricity of their orbits. 

According to the heathen mythology, Vesta 
was the sister and wife of Saturn ; and her daugh- 
ter, called Vesta the Younger, the reputed god- 
dess of Chastity, was represented by no image, 
but a perpetual fire was maintained on her altar, 
which was carefully attended by virgin priest- 
esses, called Vestals. Hence modern astronomers 
have adopted the figure of an altar with a fire 
blazing upon it, as her emblem, g. 



SEC. 15. 

JUNO. 

Juno was discovered by M. Harding, of Lili-en- 
thal, near Bremen, on the 1st September, 1804. It 
revolves round the sun in rather less than 1591 



CERES. 251 

days, at the mean distance of 254,000,000 of miles. 
At its aphelion point it is five-thirds the distance 
from the sun that it is at the perihelion ; and its 
orbit crosses those of the other three asteroids, 
though not in the same plane. The diameter of 
this planet is stated at 460 miles ; its orbit has an 
inclination to the ecliptic of somewhat more than 
13°. It is invisible to the naked eye, but through 
a telescope it has a resemblance to a star of the 
eighth magnitude. 

Juno, among the mythologists, was the sister 
and wife of Jupiter, and queen of heaven; and she 
had names as numerous as any of the heathen dei- 
ties. The peacock was sacred to her ; and Iris 
(the rainbow) was her constant attendant. Al- 
though now translated into a planet, she seems to 
have been originally the lonah (messenger) or 
dove of Noah, who brought to that patriarch the 
olive-leaf, emblematical of the restoration of the 
divine favour towards the human race. Her as- 
tronomical emblem is by some a sceptre surmount- 
ed with a star, token of magnificence, f ; by 
others, a mirror, crowned with a star 0> the em- 
blems of beauty and power. 



SEC. 16. 

J CERES. 

Ceres was discovered by M. Piazzi, of Palermo, 
in Sicily, on the 1st January, 1801. Her mean 



252 PALLAS. 

distance from the sun is nearly 263,000,000 of 
miles, and she performs her annual revolution in 
1081 days. There is very little difference be- 
tween the aphelion and perihelion points of this 
planet; but its orbit, which inclines to the ecliptic 
rather more than 10^°, is crossed by the orbits of 
Juno and Pallas. The diameter of this planet is 
460 miles : it is much too small, at such a dis- 
tance, to be discovered by the naked eye ; and 
through a telescope it appears like a star of the 
eighth magnitude, resembling Mars in colour. 

Ceres, in idolatrous times, was the reputed god- 
dess of Corn and Harvests, the daughter of Saturn 
and Vesta, and mother to Proserpine. She was 
held in great veneration ; and, among a variety 
of other titles, had that of Bona Dea, the benefi- 
cent goddess. Her emblem, among astronomers, 
is a sickle, 5, the instrument of the harvest. 



SEC. 17. 

$ PALLAS. 

Pallas was discovered by Dr. Olbers, of Bre- 
men, on the 28th March, 1802. It moves between 
Mars and Ceres at the distance of nearly 
263,000,000 of miles from the sun; completing its 
annual revolution in rather less than 1682 days. 
The diameter of this planet is 670 miles. The 
aphelion point of this planet is about once and a 



THE ASTEROIDS. 253 

half as distant from the sun as its perihelion : its 
orbit crosses the orbits of the other three aste- 
roids; and its inclination to the plane of the eclip- 
tic is prodigiously great, being about 34^°, which 
is far beyond the limits of the zodiacal belt. 

Among the mythologists, Pallas, the same with 
Minerva, was the daughter of Jupiter, from whose 
brain she was fabled to have sprung completely 
armed, and brandishing a spear. She w 7 as the 
reputed goddess of Wisdom ; and the owl and the 
cock were her favourite birds. The olive-tree 
was also sacred to her. She was likewise the 
patroness of the Liberal Arts. Her astronomical 
emblem is the head of a spear, $. 



SEC. 18. 

GENERAL REMARKS CONCERNING THE ASTEROIDS. 

Dr. Olbers had conceived the idea that Ceres 
might possibly be the fragment of a larger planet 
which formerly revolved between the orbits of 
Mars and Jupiter, and had been burst asunder by 
some unknown powerful force, and that other 
bodies similar to these three were yet to be found. 
This idea, whether correct or not, appears to have 
led to the discovery of the other three asteroids. 
Thus, four primary planets belonging to our sys- 
tem, were discovered in a little more than six 
years. 



254 THE ASTEROIDS. 

It is quite remarkable, that the possibility 
of the existence of a planet between Mars and 
Jupiter had been previously conjectured, by Pro- 
fessor Bode, of Berlin, on the ground that the suc- 
cessive intervals between the orbits of the planets 
vary pretty nearly according to a certain law ; 
while the interval between Mars and Jupiter 
forms the only exception, being much too great, 
and requiring a planet of the mean distance of the 
asteroids to make the series complete, If a planet 
having this mean distance should have exploded 
by any internal force, the fragments must, on 
making a period, return near the same portion of 
space in the solar system. It was by searching 
in this portion of space that the three last asteroids 
were discovered. So carefully were the heavens 
w r atched for the first twenty years of the century 
by the German astronomers, that Dr. Olbers states 
with confidence that no asteroid of the eighth 
magnitude could have traversed that region with- 
out being discovered. 

We have but a very imperfect knowledge of the 
magnitudes of these planets, and none respecting 
their rotations and the positions of their axes. 
Lamont has determined the probable diameter of 
Pallas to be about 670 miles. This is the largest 
of the four, and Vesta is the smallest ; its surface 
being estimated at 229,000 square miles, or about 
one-tenth of the surface of the United States. 

Our information concerning these small bodies is confined 
to the elements of their orbits, and other circumstances de- 



THE ASTEROIDS. 



255 



pending on these elements. The orhits of Pallas and Juno 
are very eccentric; and, consequently, the intensity of light 
and heat, and the apparent magnitude of the sun, are very 
different for them in different parts of their course. The fol- 
lowing table will show the maxima and minima values of 
these quantities, the average intensity of the light received at 
the earth being called 100. 



Vesta 
Juno 
Ceres 
Pallas 


Intensity of Light in the 


Apparent Diameter of the Sun in the 


Perihelion. 


Aphelion. 


Perihelion. 


Aphelion. 


22 

26 
16 
23 


15 

9 

11 

8 


14'53\8 

16 9 .8 
12 32 .5 
15 12 .6 


12' 26".2 
9 32 .1 

10 43 .4 
9 17 .6 



Another peculiarity of the orbits of these planets is, theii 
great inclination to the orbit of the earth, or ecliptic. The 
orbit of Vesta is inclined 7° 8'; th t of Juno, 13° 4'; that of 
Ceres, 10° 37'; and that of Pallas, 34° 35': so that they will 
sometimes be found beyond the limits of the zodiac, and have 
for that reason been called the ultra-zodiacal planets. 

These planets revolve around the sun at nearly the same 
mean distances, in round numbers, as follows : 

Vesta 225 millions of miles. 

Juno 254 " " 

Ceres . , 263 " " 

Pallas 263 " " 

Their terms of revolution are — Vesta, 1325 days; Juno, 
1591 days; Ceres, 1681 days; and Pallas, 1682 days. This 
is a very different arrangement from that of the other planets, 
whose mean distances and times of revolution are immensely 
different; whilst two of these, Ceres and Pallas, have nearly 
the same mean distance, and their periods differ hardly a 
single day. These two planets, thus revolving around the 
sun almost at the same mean distance, and in the same time, 
present a singular anomaly in the solar system ; they do not, 
however, move in the same, or nearly the same, path — their 
elliptic orbits being of verv different forms ; that of Pallas 



256 



THE ASTEROIDS. 



much more elongated than that of Ceres, and the two paths 
lying in planes very differently inclined. 

The brightest star visible in their heavens is 
Jupiter, at his opposition; when this occurs at 
the time of the aphelion of Pallas, he will appear 
at that planet 2^ times larger than he ever does 
to us, and will be within 170 millions of miles of 
Pallas, who will then receive from him six times 
as much light as we ever do. The other three 
planets can never be nearer to Jupiter than from 
220 to 340 millions of miles. 

For observations of the inferior planets, Mercury, Venus, 
the Earth, and Mars, these planets are as unfavourably situ- 
ated as the earth is for observations of Mercury. The transits 
of these inferior planets over the sun's disc will occur very 
seldom, on account of the small apparent diameter of the 
latter, and the great inclination of the orbits of the small pla- 
nets. For Juno and Pallas there will hardly be one in a cen- 
tury of our years. Saturn and Uranus, in opposition, appear 
somewhat larger there than at the earth. 

The force of gravity at the surfaces of these bodies must 
be very small. If we suppose them to be of the same den- 
sity as Mercury, which is the most dense, so far as is known, 
of all the planets, then, supposing the diameters to be as in 
the following table, we shall have : 



Vesta 
Juno 
Ceres 
Pallas 


Diameters. 


Fall in the first Second 


Length of the Seconds Pendulum. 


270 miles 
460 " 
460 " 
670 " 


7 inches 

11 " 

11 " 

16 " 


1 inch 

2 " 

2 " 

3 " 



The weight of a pound at the earth weuld there be only 
about an ounce ; and the physical power of an inhabitant of 
the earth would enable him to accomplish wonders upon one 
of these planets. 



JUPITER. 257 

SEC. 19. 

^JUPITER. 

Jupiter, the largest orb in our system, with the 
exception of the sun, is about 91,000 miles in dia- 
meter, and occupies 11 years 315 days 14^ hours, 
nearly, in performing his circuit about the sun, 
from which he is distant upwards of 494,000,000 
miles, travelling at the rate of 28,000 miles in an 
hour. 

This planet is full five times as far from the 
sun as the earth is. Its revolution on its axis 
is accomplished in 9 hours 55 minutes 26^ seconds 
— a rotary velocity twenty-five times that of the 
earth. Hence its year consists of 10,477 Jovian 
days. In consequence of this swift diurnal rota- 
tion, the equatorial diameter of Jupiter is 6000 
miles greater than his polar diameter. 

The density of Jupiter is not quite one-fourth 
of that of the earth, and a little greater than that 
of water. Hence, although Jupiter is 1300 times 
as large as the earth in bulk, its mass of matter, 
or weight, is only about 300 times as great. 

The attracting mass of Jupiter being 300 times 
the earth's, and his semi-diameter being eleven 
times as great as ours, gravity at his surface will 
be only 2^ times that of ours. In other words, a 
pound here would weigh 2^ pounds there. 



258 JUPITER. 

There is, however, a great difference in the weight of bo- 
dies on different parts of the surface of this planet, in conse- 
quence of its being very much flattened or compressed at the 
poles. This compression amounts to nearly ^ of its diameter, 
its polar being only -|4 of its equatorial diameter. This differ- 
ence is perceptible with the aid of a good telescope, the disc 
appearing not perfectly round, but slightly oval, or a little 
elongated in the direction of the satellites, which are always 
seen in the direction of its equator. (See the Frontispiece.) Hence 
a body at the pole, being much nearer the centre of Jupiter, 
will weigh much more than the same body would at the 
equator. 

There is, moreover, another cause of difference between 
the force of gravity at the equator and that at the poles. This 
is, the rapid revolution of the planet about its axis. The 
equatorial regions move in the circumference of a circle at 
the surprising velocity of nearly 28,000 miles an hour — the 
effect of which is to produce a very great centrifugal force, or 
tendency to fly off from the centre, in bodies near the equator. 
This counteracts, in part, the gravity of those bodies; whilst, 
at the poles, the weight of bodies is not at all diminished by 
this cause. The combined effect of these two causes is, that 
a body will weigh three-tenths more at the pole of Jupiter, 
than at its equator. There must, of course, be a correspond- 
ing variation in the length of the pendulum on different parts 
of the surface of this planet. In fact, a pendulum vibrating 
seconds, at the equator, would be 34.9 feet, and at the poles 
45.2 feet, in length ; or nearly one-third longer than that at 
the equator. 

The inclination of the equator of Jupiter to his orbit is only 
3° 5'; and the eccentricity of the latter being very small, the 
difference of the seasons will be but slight; and that of the 
lengths of days at different seasons of the year will also be 
very small, compared with the earth; for the variation in the 
meridian height of the sun, at any given place, throughout 
the year, cannot exceed 6° 10'. 



JUPITER. 259 

Longest Day. Shortest Day. 

In latitude 40° 5hT 6m. 26s 4h749m. 14s. 

" 60 5 15 47 ... . 4 39 53 

It is only within 3° 5' of the poles that the sun can remain 
invisible during any entire revolution of the planet about its 
axis. 

The intensity of the light and heat of the sun at Jupiter is 
2^ of that at the earth, and the sun appears there under an 
angle of 6' 10"; or his apparent diameter, when seen from 
Jupiter, is about one-fifth as great as when seen from the 
earth. 

The ecliptic and equator of Jupiter lie nearly in the same 
plane as our ecliptic. In consequence of the rapid motion of 
this planet, the sun and stars will appear to move from the 
eastern to the western horizon in a little more than five hours, 
or 2J times faster than in our firmament; so that the appa- 
rent motion of all these bodies, except the stars near the poles, 
will be rendered perceptible to the eye, by a contemplation 
of them, for only a few moments. This constitutes one of 
the most interesting peculiarities in the firmament of Jupiter. 

The view of Saturn from Jupiter will be better than from 
any other planet. Saturn will appear 40", and his ring 90", 
in diameter ; or one-twentieth as large as we see the sun, and 
one-fourth as large as it appears from Jupiter. The transits 
of the inferior planets over the sun's disc will be more fre- 
quent, but more difficult to observe at Jupiter than at our earth. 
Jupiter exceeds all the other planets in bright- 
ness (except sometimes Venus), and may thus be 
easily distinguished. When viewed through a 
telescope, his disc is perceived to be surrounded 
by faint cloudy stripes, called zones, or belts, 
which, though generally parallel to his equator, 
are subject to great variations both in figure and 
number. Sometimes eight have been seen at once, 
sometimes only one : sometimes they continue for 



260 JUPITER. 

three months with little or no variation, and some- 
times a new belt has been formed in less than two 
hours. From their being subject to such changes, 
Dr. Brewster suggests that the atmosphere of 
Jupiter reflects more light than the body of the 
planet; and that the clouds which compose it, 
being thrown into parallel strata by the rapidity 
of its diurnal motion, form interstices through 
which the opaque body of the planet becomes 
visible. 

The face of Jupiter is also covered with spots, 
which, however, from the variations of some of 
them, and the sensible difference in the period of 
their rotation, induce an opinion that they are 
only clouds, which the winds transport with va- 
rious degrees of velocity, in an extremely agitated 
atmosphere. Sometimes one or more spots are 
formed between the belts, which increase till the 
whole are united in a large dusky belt. 

Besides these cloudy indications, some bright 
spots are to be discovered on the surface of this 
planet, of a more permanent nature, though sub- 
ject to disappear and reappear after unequal in- 
tervals of time. The remarkable spot, by whose 
motion the rotation of Jupiter on his own axis 
was first ascertained, disappeared in the year 
1694, and was not again seen till 1708, when it 
reappeared exactly in the same place, and has 
been occasionally seen ever since. 

Upon the whole, the appearance of Jupiter 
through a telescope is of the most interesting na- 



JUPITER. 261 

ture, and opens a vast field for curious inquiry. 
(See Frontispiece.) 

Jupiter is attended by four satellites, or moons, 
which revolve about him at different distances, 
and in different periods of time. They were first 
discovered by Galileo, and are visible with a tele- 
scope of moderate magnifying power, nearly in a 
line with the belts on the planet. The nearest of 
these satellites makes a revolution in less than 
two days, and the most distant in rather less than 
seven. From these revolutions, it is evident the 
satellites, like our moon, are liable to be eclipsed; 
and, by means of their eclipses, a method has 
been devised for determining the longitude of 
places with great facility and accuracy. By the 
same means, also, is demonstrated the progressive 
motion of light; the velocity of which is more 
than a million of times greater than that of a ball 
issuing from a cannon. # 

The greatest ornament of the nocturnal heavens 
of Jupiter is his group of four moons, or satellites. 
Their apparent diameters, as seen from the pla- 
net, are 31' 11", 17' 35", 18' 0", and 8' 46"; the 
first appears nearly as large as our moon. They 
may sometimes all be seen above the horizon of a 

* Rays of light pass from the sun to the earth in about 
eight minutes and a half, or at the astonishing rate of 11,500,- 
000 miles in a minute. If the sun were suddenly annihilated, 
we should continue to see him for eight minutes and a quarter 
afterwards ; and if recreated, we should not behold him till 
eight minutes and a quarter afterwards. 
18 



262 JUPITER. 

given place at once ; but they will much oftener 
all be invisible. 

The following drawing shows the telescopic 
appearance of Jupiter and his satellites as seen 
from the earth. 




Owing to the proximity of these satellites to 
their primary, they can never see quite half of his 
surface at a time. The portion visible at the first 
is 0.414; that at the second, 0.446;. that at the 
third, 0.466; and that at the fourth, 0.481. Ju- 
piter is robbed of the best portion of the light of 
his moons — viz., that of the full moons — by 
eclipses. 

The satellites revolve from west to east, in planes very 
nearly coincident with that of the equator of the planet. The 
latter plane, being inclined only about 3° to the orbit, differs 
very little from the plane of the ecliptic. Hence, when viewed 
from the earth, these satellites appear to oscillate to and fro, 
sometimes passing across the body of the planet, and casting 
shadows upon his disc ; and at others disappearing behind 
the body, or falling into its shadow, at a distance from the 
planet. In the former case, Jupiter suffers a solar eclipse ; 
and, in the latter, his moons are eclipsed. (See the figure 
of Jupiter and his satellites.) 



JUPITER. 263 

The first three satellites are eclipsed at every opposition, 
or full moon; the fourth may occasionally esca being 
eclipsed, owing to the greater inclination of its orbit: this 
escape, however, occurs very rarely, and all the four moons 
are eclipsed at nearly every revolution. The first, or nearest 
satellite, is totally eclipsed every 42J hours. 

Notwithstanding the number of Jupiter's moons, 
the earth is better provided with moonlight than 
that planet ; for, as has been before stated, the 
intensity of the light of the sun is only ^ as great 
there as at the earth; and moreover the first satel- 
lite presents a disc about the size of our moon; 
the discs of the second and third are about one- 
third, and that of the fourth only one-twelfth, as 
large : so that their combined light would not be 
equal to that of our one moon. 

There are some portions of the surface of Jupiter which 
have no moonlight. At the 81st degree of latitude, the first 
satellite is never seen; at 84 J°, the second is never visible; 
at 864°, the third ; and at 88°, none of them can ever be seen. 
It is only in the equatorial regions that the moons are of 
material benefit. 

The arc which Jupiter describes by his geocentric retro- 
grade motion, is about 10°; and the time occupied in describ- 
ing it is 119 days. The retrograde motion begins and termi- 
nates when Jupiter's elongation from the sun is about 115°. 

The heavenly bodies which may be observed 
from Jupiter, independently of the sun and fixed 
stars, are: his own satellites — the planet Saturn, 
with his ring and satellites — and probably Her- 
schel, w T ith his satellites. 

Jupiter, among the heathens, was the reputed 



264 JUPITER. 

son of Saturn and Rhea, brother and husband to 
Juno, and king of heaven and earth. His wor- 
ship was universal, and surpassed in solemnity 
that of all the other deities. His temples were 
numerous, and he had many oracles, of which the 
most renowned were those of Dodona, in Epirus, 
and Ammon, in the Libyan Desert. His names 
were numerous; as Osiris, Ammon, Baal, Belus, 
Zeos, Dios, Jeu, Jeud, Thor, Sanus, Olympius, 
&c. The oak and the eagle were sacred to him ; 
and he was generally represented on a splendid 
throne of gold or ivory, with lightning and thun- 
derbolts in one hand, and a sceptre of cypress in 
the other: his look was majestic; his beard long 
and flowing; and at his feet stood the eagle with 
expanded wings. His name seems to be formed 
of Io or Ion, the dove, and Pater, lord or priest ; 
and his character appears to have been twofold : 
as lord of the dove, or heavenly messenger, which 
brought to the remnant of the human race, shut 
up in the Ark, the good news of divine reconcilia- 
tion, he was an idolatrous representative of the 
true God ; and as priest of the dove he may be 
easily referred to Noah, who offered the first sacri- 
fice after the general Deluge. There were many 
Jupiters: Varro reckons three hundred, Diodorus 
mentions two, and Cicero three ; but the actions 
of all were attributed to the son of Saturn and 
Rhea, who was said to have been born in Crete, 
and to have reigned on Mount Olympus, between 
Macedonia and Thessaly. The character used by 



SATURN. 



265 



astronomers to designate Jupiter, seems originally 
to have been the letter Z, the first letter of Zeus, 
the Greek name of Jupiter; which in the course 
of time has been changed to %. 



SEC. 20. 



h SATURN. 



The tenth planet in order from the sun, moves 
in an orbit which, during many ages, was consi- 
dered as the boundary of our system. His mean 



SATU 




distance from the sun is upwards of 906 millions 
of miles, or more than 9J times that of the earth. 
His diameter is 79,000 miles, and his magnitude 
almost a thousand times that of the earth. His 
annual revolution occupies nearly 10,759 days, or 
about 29i of our years, although he moves at the 
rate of little short of 21,000 miles every hour. 
His rotation upon his own axis from west to east 
is performed in 10 hours 30 minutes ; consequently 



266 SATURN. 

he has more than two days to our one. His orbit 
inclines to the ecliptic almost 2J degrees ; and his 
axis is inclined to the plane of his orbit 29 de- 
grees. He shines with a pale lead-coloured light ; 
and the proportion of his polar to his equatorial 
diameter is as 10 to 11. 

Saturn is by far the most wonderful and mag- 
nificent member of the solar system. Its apparent 
diameter, or the angle it subtends, as seen from 
the earth, is 16", or about T ^, as great as that of 
the moon. This stupendous globe, besides being 
attended by no less than seven moons, is surrounded 
with two broad, flat, rings, extremely thin, and 
nearly concentric with the planet. 

They lie in the same plane, and are separated from each 
other by a very narrow interval. That which separates the 
inner ring from the body of the planet is much wider. The 
thickness of this extraordinary appendage, according to the 
younger Herschel, does not exceed 100 miles. The other 
dimensions, as derived from the observations of Struve, are 
as follows : 

Exterior diameter of exterior ring 176,418 miles. 

Interior diameter of exterior ring 155,272 " 

Exterior diameter of interior ring 151,690 " 

Interior diameter of interior ring 117,339 " 

Equatorial diameter of the body 79,160 " 

Interval between the planet and interior ring 19,090 " 

Interval between the rings . . . . ; 1,791 " 

A telescopic view of Saturn is given in the 
frontispiece. It is surrounded by its rings, and 
its body is striped with dark parallel belts resem- 
bling those of Jupiter, but less strongly marked, 




Phases of Saturn* 



SATURN. 267 

and owing, doubtless, to a simi ar cause. That 
the ring is a solid opaque substance, is evident 
from the fact that it casts a shadow upon the side 
of the planet nearest the sun, and on the opposite 
side the ring receives the shadow cast by the body 
of the planet, as represented in the figure. From 
the parallelism of the belts with the plane of the 
ring, it might be conjectured that the axis about 
which the planet revolves is perpendicular to that 
plane; this is found to be the case by observa- 
tions of spots which are occasionally seen upon 
its surface, the motions of which indicate a rota- 
tion about such an axis in lOh. 29m. 17s., accord- 
ing to Herschel ; this period is, however, some- 
what uncertain. 

The axis of Saturn, like that of the earth, pre- 
serves its parallelism to itself during the revolu- 
tion of the planet round the sun. (See the draw- 
ing.) The rings rotate about the planet, in the 
plane of its equator, in nearly the same time as 
is occupied by the planet in making a revolution 
about its axis. 

Their plane, which is always parallel to itself, is inclined 
to the ecliptic at an angle of 28° 39' 45" ; and it intersects 
the ecliptic in two opposite points, called the nodes of the ring, 
whose longitudes or distances from the vernal equinox, are 
70° and 350° respectively. In consequence of this obliquity 
of position, the rings always appear elliptical to us, with an 
eccentricity so variable that they occasionally appear like a 
straight line crossing the body of the planet. In the begin- 
ning of October, 1832, the plane of the rings passed through 
the centre of the earth, so that the edge was turned directly 



268 SATURN. 

towards us; in that position it is visible only with the most 
powerful telescopes, and appears like an extremely fine line 
crossing- the disc of the planet, projecting out a little distance 
on each side of it. The rings are in this position twice dur- 
ing every revolution of Saturn round the sun, or at intervals 
of about 15 years, near the time when the planet is in the 
longitude of one of the nodes of the ring. At that time the 
plane of the ring passes through the centre of the sun, and 
the edge only is illuminated : this phenomenon occurred 
about the middle of December, 1832. The earth generally 
passes through the plane of the ring twice within a few 
months of the time when the planet is in longitude 170° or 
350°; accordingly the rings vanished again in the end of 
April, 1833. As the planet recedes from one of these points 
of its orbit, the line of sight becomes gradually more and 
more inclined to the plane of the ring, which appears to open 
out by degrees into an ellipse which attains its greatest 
breadth when the planet is 90° distant from one of these 
nodes, or in longitude 80° or 260°. At the time of its great- 
est opening, the longest diameter is just twice as great as the 
shortest. The figure represents the form of the ring as seen 
from the earth, E, at different periods, throughout a revolution 
of Saturn round the sun, S. 

It is a singular result of theory that the rings 
could not maintain their stability of rotation, if 
they were everywhere of uniform thickness and 
density ; for the smallest disturbances would de- 
stroy their equilibrium, which would become more 
and more deranged, till, at last, they would be 
precipitated on the surface of the planet. They 
must therefore be irregular solids, so that their 
centres of gravity do not coincide with the cen- 
tres of their figures. Professor Struve has disco- 
vered that the centre of the ring is not exactly 



SATURN. 269 

coincident with the centre of Saturn, the angular 
distance between the two centres being about J of 
a second. 

The rings of Saturn must present a most mag- 
nificent spectacle in the firmament of that planet, 
as vast arches or semicircles of light extending 
from the eastern to the western horizon, occupy- 
ing a large portion of the visible sky. Their ap- 
pearance varies in different regions of the planet. 
At about 37° distance from the equator, on the 
side towards the sun, they are seen in their great- 
est splendour, as semicircles stretching across the 
heavens. In the daytime they appear dim, like a 
cloud, or like our moon when the sun is above the 
horizon. After sunset their brightness increases, 
and the shadow of the planet is seen on the east- 
ern part of the ring directly opposite the sun ; as 
the night advances, this shadow moves gradually 
along the ring till it disappears in the west at 
sunrise. On the equator, only the inner surface 
of the interior ring is visible as a very narrow 
belt extending from the eastern through the zenith 
to the western point of the horizon. In the polar 
regions of the planet only a small portion of the 
rings is visible, and at the poles they are never 
seen. 

During half of Saturn's year, or nearly fifteen 
of our years, the sun shines on one side of the 
rings without intermission. The portion of the 
surface of the planet on that side of the equator 
is, therefore, enlightened by the sun in the day- 



270 SATURN. 

lime, and by the rings at night, while the portion 
of the other hemisphere lying under the dark side 
of the ring, suffers a solar eclipse of fifteen years' 
continuance. 

Saturn's very long year of 10,759 terrestrial days consists 
of 24,591 Satumian days. It is divided into four seasons, as 
follows : 

Northern Hemisphere. Southern Hemisphere. Terrestrial Years. 

Spring Autumn 7.74 

Summer Winter 8.01 

Autumn Spring 6.94 

Winter Summer G.76 

The intensity of light at Saturn is from 81 to 101 times as 
weak as at the earth. The apparent diameter of the sun 
varies from 3' 33,2", to 3' 10.6"; or, it is a little more than 
y'q his diameter as seen from the earth. 

The force of gravity at the surface of the earth being called 
100, that at the pole of Saturn is 135 ; the fall of a body 
during the first second is 21.664 feet, and 1 pound weighs 
there 1 pound 5 J ounces. At the equator, in consequence of 
the compression of the planet at the poles, and its rapid rota- 
tion, the fall is 12.384 feet in the first second, and a pound 
only weighs 12J ounces. The length of the seconds pendu- 
lum is 2.51 feet at the equator, and 4.39 feet at the poles ; so 
that the observations of the length of the pendulum affords 
to the inhabitants of that planet a good means of determining 
Saturnigraphical latitudes. 

The apparent diurnal motion of the heavens is 
nearly as rapid for Saturn as for Jupiter, and for 
each place on the surface of the former planet, a 
certain zone of stars will be constantly eclipsed 
by the rings, except in the polar regions, where 
the rings are invisible. 




The nocturnal heavens of Saturn are adorned 
by seven satellites, whose diameters are quite un- 
known to us, but we may with some degree of 
certainty assume, that their united discs, as seen 
from Saturn, would not form one as large as that 
which our moon presents to us. 

The diameter of the most distant satellite but 
one (sometimes called the Huygenian Satellite,) 
has been estimated at about 2700 miles ; hence it 
appears at Saturn under an angular diameter of 
8' 40" ; supposing the last or most distant moon 
to be of the same magnitude as of the Huygenian, 
its apparent diameter would be only 3". 

In reference to the phases which these moons present to 
their primary, they differ essentially from the satellites of Ju- 
piter and our moon. With the latter, the inclination of their 
orbits to those of the primaries is too small to produce any 
remarkable difference in the various phases at different sea- 
sons of the year. But it is not so with Saturn ; it never has 
a perfect full moon or a perfectly invisible new moon, except 
at those seasons of its year when it is near one of the nodes 
of the plane of its ring, which is nearly the plane of the 
orbits of its moons ; at all other seasons there remains at the 



272 SATURN. 

opposition of either of the moons, a small portion of the 
northern or southern border of the disc of the moon unillu- 
minated, and when the moons are in conjunction, a small 
portion of the northern or southern border is illuminated. 
The breadth of this part is at a maximum when Saturn is 
90° from the nodes of its rings. 

As is well known, our moon passes the meridian of a given 
place, about 50 minutes later each night than the preceding, 
owing to its motion being in a direction opposite to that of 
the apparent daily motion of the heavens. The first or near- 
est satellite of Saturn revolves around that planet in 22| hours, 
in a direction opposite to that in which the heavens appear to 
make a revolution in 10J hours, so that when this satellite, 
as a full moon, passes the meridian of any place on the sur- 
face of Saturn at midnight, it will not come to that meridian 
again until 19f hours afterwards, or the second night after, at 
If hours before midnight. Or, in other words, the first satel- 
lite of Saturn passes the meridian of a given place at inter- 
vals of a little less than two of Saturn's days. 

Owing to the great inclination of the ring and of the orbits 
of the satellites to the ecliptic, or orbit of Saturn, the eclipses 
of the moons can happen only at those seasons when the 
planet is in the neighbourhood of one of the nodes of the 
ring. During a period of 6J of our years, at the middle of 
which time Saturn is in one of these nodes, the innermost 
satellite is eclipsed every full moon ; and for about 8j years, 
preceding and following this period, it cannot be eclipsed. 
The periods during which eclipses of the other satellites will 
occur, are much smaller; for the Huygenian, or sixth satel- 
lite, it is only one year ; and for a period of 13.7 years, or 
nearly a half of Saturn's year, it suffers no eclipse. Eclipses 
of the sun, caused by these satellites, are phenomena of 
almost daily occurrence, about the time when Saturn is in 
one of the nodes of its ring. 

These seven satellites, owing to their great dis- 
tance from us, appear much smaller than those of 



SATURN. 273 

Jupiter, and for their observation much larger 
telescopes are requisite. Their theory is for the 
same reason less perfect. The most distant satel- 
lite is the largest, it being probably not much less 
than Mars. Its surface, like those of the satellites 
of Jupiter, presents a varying light, from observa- 
tions of which it has been concluded that it per- 
forms a revolution about its axis and one about 
Saturn in the same period of time. The plane of 
its orbit is sensibly inclined to the plane of Sa- 
turn's ring, whilst the planes of the other orbits 
lie very nearly in the plane of the ring. The 
sixth satellite is next to the seventh in magnitude. 
The others are very much smaller, and the first 
three so small as only to be visible through the 
very largest telescopes, and even with such instru- 
ments they can only be seen under the most fa- 
vourable circumstances. Sir William Herschel 
has seen them at a time when the ring had disap- 
peared to all other observers ; but they appeared 
to him, through his great telescope, as extremely 
small bright spheres upon a very fine line of light. 
The times of revolution of these satellites, and 
their mean distances from Saturn in terms of his 
equatorial semi-diameter, are given below. 

1 Satellite 
2 



Time of 
Od. 22h 


Revolu 
36m 
53 
18 
45 
25 
41 
55 


tion. 

18s 


Mean Distance. 
2.4682 


1 8 
1 21 


3 .... 


3.2079 

5.284 


2 17 




6.819 


4 12 




9.524 


15 22 


25 


20.7060 


79 7 




64.359 



274 SATURN. 

The orbits of the third, fourth, fifth and seventh, 
are but little known ; those of the first and second 
somewhat better ; and that of the sixth best of all. 
That of the second has no sensible eccentricity. 
The eccentricity of the first is 0.06889 ; and the 
longitude of the point nearest Saturn is 104° 42'. 

In the language of the mythologists, Saturn was 
the son of Uranus, otherwise Ccelus, and Terra, 
i, e. of Heaven and Earth, and the father of Vesta, 
Ceres, Pluto, Neptune, Jupiter, and Juno. His 
reign is represented as so mild, beneficent, and 
virtuous, that it obtained the title of the golden 
age. He is generally represented as a decrepit 
old man, holding in his right hand a scythe, and 
a serpent in a circular form biting its own tail, — 
emblems of the ravages of time and the revolution 
of the year. In his left hand, he holds a child, as 
if about to devour it, to denote that time con- 
sumes its own productions. He also bore the 
names of Sator, Ilus, and Chronus; and his festi- 
vals, called Saturnalia, were celebrated about the 
time of the winter solstice, to commemorate the 
freedom and equality which prevailed on earth 
during his reign. Some have supposed that Sa- 
turn was an apotheosis of the patriarch Noah, 
others of his son Ham ; but Macrobius assures us 
that his name was a Phoenician title of the sun. 
The astronomical sign of Saturn, T^, is supposed 
originally to have represented a scythe. 



URANUS. 275 

SEC. 21. 

J£t HERSCHEL, OTHERWISE URANUS, OR GEORGIUM SID US. 

This planet was discovered by Sir William 
Herschel, on the 13th of March, 1781. In honour 
of his royal patron, George III., he gave it the 
name of Georgium Sidus, or Georgian Star; but 
by foreigners it is frequently called Herschel, in 
honour of its discoverer ; and the Royal Academy 
of Prussia, with some others, called it Uranus, 
from the circumstance of the other planets being 
named from such heathen deities as were reputed 
relatives : thus Uranus was the father of Saturn, 
Saturn the father of Jupiter, Jupiter the father of 
Mars, &c. Pleasing as this analogy may appear, 
the appellation of Herschel is quite as appropriate, 
inasmuch as it is an honour justly due to the in- 
genious and persevering discoverer. 

Herschel is the most remote planet yet disco- 
vered in our solar system. He is rarely to be 
seen but through a telescope ; but in a clear night, 
when the moon is absent, he may be seen by the 
unassisted eye, about the size of a star of the sixth 
magnitude, of a bluish white colour, with a bril- 
liancy between that of Venus and the moon. 

The mean distance of this planet from the sun 
is upwards of 1,822,000,000 of miles, or about 19 
times the distance of the earth. His diameter is 
variously stated at 34,170 and 35,865 miles, and 



276 URANUS. 

his bulk is 80 times as great as that of our earth. 
He moves nearly in the plane of the ecliptic, the 
inclination of his orbit being somewhat less than 
46^ minutes. 

This planet performs his annual revolution in 
nearly 30,689 days, or rather more than 84 of our 
years, moving from west to east at the rate of 
15,546 miles per hour. His rotation upon his 
axis is performed in about If of our days. 

Our knowledge of this, the most distant planet 
of the system, is too limited to enable us to give 
a very detailed account of its peculiarities. It 
receives from the sun, when nearest that body, 
3^ T , and when most distant T ±j as much light as 
the earth. 

The apparent diameter of the sun, as seen from Uranus, 
or Herschel, varies from 1' 36" to 1' 45"; the apparent disc 
of the sun is only ^^ as great there as at the earth. Its 
light at that planet is about midway between our sunlight 
and our moonlight. 

The situation of Uranus is unfavourable for obtaining a 
knowledge of the solar system. Even Saturn appears at 
Uranus smaller than at any other planet of the system, and 
Jupiter appears hardly as large there as Mercury does to us. 
All the other planets are, with reference to Uranus, inferior, 
and may occasionally be observed from that planet upon the 
sun's disc; these transits are, however, of very rare occur- 
rence ; a transit of Saturn will not happen oftener than once 
in 10,000 of our years. The moons of Uranus and the fixed 
stars are the only bodies visible in his midnight heavens. 

Vast as is the distance of Uranus from the earth, it must 
not be supposed that the fixed stars appear larger or nearer 
than they do to us ; for the distance of this planet from the 



URANUS. 277 

earth is less than one thirty- thousandth part of that of the 
nearest fixed star known ; the former distance is to the latter 
what the height to which an aeronaut soars is to the distance 
of the moon. 

The annual parallax of the fixed stars, or, the 
angle contained between two lines conceived to be 
drawn from a star, one to the sun and the other 
to the planet, is nineteen times greater for Uranus 
than for the earth. This angle is, for the nearest 
fixed star, but a small fraction of a second at the 
earth, whilst at Uranus it amounts to several 
seconds. So that the problem of finding the An- 
nual parallax and distance of the fixed stars, 
which so long baffled all the attempts of our astro- 
nomers to solve it, but which at last yielded to 
the genius of Bessel, presents very little difficulty 
to the Uranians, except that which arises from 
the length of one of his years, required to com- 
plete an observation. This is the only point in 
which the latter astronomers have an advantage 
over those of our earth. 

The greatest peculiarity of the Uranian system is that the 
orbits of the satellites are nearly perpendicular to that of their 
primary, and their motions are in a retrograde direction, that 
is, from east to west; while the satellites of all the other 
planets revolve from west to east around their primaries, in 
paths but slightly inclined to those of the latter. 

We have already seen that, in the variation of their phases, 
the moons of Saturn differ from those of Jupiter and the 
earth ; but this difference is very small in comparison with 
that which the position of the paths of the satellites of Ura- 
nus causes in their phases when compared with those of Ju- 
piter and the earth. When the planet is near 90° from the 
19 



278 URANUS. 

node of the orbit of one of its moons, that moon will be con 
tinually in quadrature, or nearly so, and will present either a 
little more or a little less than half its illuminated side to- 
wards its primary, during a period of several revolutions of 
the satellite : its phase will be nearly like that which our 
moon presents a day before or after its quarter. On the other 
hand, when Uranus is at or near one of the nodes of the 
lunar orbit, the moon will present to it the same succession 
of phases each revolution, as our moon presents to us. At 
that time also, Uranus may experience eclipses of that moon, 
and eclipses of the sun by it. 

In consequence of the positions of their orbits, these satel- 
lites suffer and cause eclipses of the sun much more rarely 
than those of Saturn or Jupiter. At intervals of a half year 
of Uranus, or about forty -two of our years, when the 
planet is at the nodes of its moons' orbits, there will occur a 
series of eclipses, which may amount, for all the moons, to 
about 200 of each kind. The first, or nearest, moon begins 
the series, and the others follow in the order of their distances 
from the primary. The whole series occupies a period of 
about two of our years, and during the succeeding interval 
of forty of our years, there are no eclipses. 

In density, Uranus is surpassed by all the other 
planets except Saturn. A pound at the earth 
weighs there 12^ ounces ; and the fall of a body 
during the first second is 12.29 feet. 

The approximate distances of the satellites, the periods of 
revolution and positions of the orbits of two of them, and 
the periods of the others, deduced by means of Kepler's third 
law, constitute our whole knowledge of these bodies. Theii 
distances and periods are as follows : 

Distances. Periods. 

1 224,000 miles 5d. 21h. 

2 291,000 " 8 16 56m. 

3 340,000 " 10 23 

4 390,000 " 13 11 9 

5 777,000 " 38 2 

6 1 556,000 " 107 17 



URANUS. 279 

The existence of the second and fourth of these moons is 
certain ; they have been observed by Lamont and the younger 
Herschel, and their orbits are pretty well determined; but 
the others have never been seen by any one except Sir William 
Herschel, and their existence is by no means certain. 

Uranus, or Ouranus, was esteemed by the hea- 
then mythologists as the most ancient of all the 
gods, although he was allowed to have had pro- 
genitors, who were also deities. His father was 
called Acmon, otherwise Eliun, or Hypsistos, and 
was worshipped under the title of the Most High; 
and his mother was Beroe, otherwise Beroth, or 
Beryth. Uranus, who also bore the names of 
Epigaeus-Autochton and Coelus, is said to have 
married his sister Ge or Terra, otherwise Tithea 
or Tellus, and was father to the Titans, Cyclops, 
and Giants, all personages of great renown in the 
mythologic legends. Though a god, he was de- 
posed by his son Saturn, one of the Titans, who 
in process of time was deposed by his own son 
Jupiter. Uranus seems to have been a personifi- 
cation of universal space, the identification of 
which with the Omnipresent Deity, there is good 
reason to believe, formed, even prior to the Deluge, 
the first heresy in religion, and led to all the me- 
lancholy results of idolatrous polytheism. The 
astronomical sign of this planet is the letter H, 
indicative of its discoverer, with the figure of a 
planet suspended from its cross-bar, W. 



280 COMETS. 



SEC. 22. 



COMETS. 



Besides the eleven planets, and their eighteen 
satellites, there is a multitude of other bodies, 
called comets, which belong to our solar system, 
and make their revolutions round our sun. They 
are called cometce, hairy bodies, or comets, from the 
appearance of their tails. 

The number of comets on record is about 500. 
Of these, the first 450 are mentioned in ancient 
annals and chronicles. The rest have been seen 
in the last hundred years, chiefly by the aid of 
the telescope. When we reflect that no comet 
was noticed by the common people from 1769 to 
1807, a period of 38 years — though 36 were seen 
in telescopes, and their orbits computed by astro- 
nomers — we readily perceive the defectiveness of 
the list. The experience of the past few years 
shows that an attentive examination of the hea- 
vens with telescopes, brings to our view about 
three comets in a year. To this number may be 
added at least one for each year, so situated with 
respect to the earth as to be invisible in its ap- 
proach to and departure from our system. Ac- 
cording to this estimate, 24,000 comets must have 
visited the solar system since the creation. When 
we extend our views farther, and consider that 
Jupiter is at the remotest distance from the sun 



COMETS. 281 

at which comets are ever visible to us, and that 
the active force of gravity of our sun extends 
through a sphere whose radius is more than a 
million of times the distance of Jupiter, we must 
conclude that the number of comets which in the 
immensity of space still obey the controlling power 
of our sun is almost countless. We may safely 
estimate them by hundreds of thousands, and pro- 
bably by millions! 

The purpose for which these singular bodies 
were created, is as little known to us as is the 
nature of their internal organization. As far as 
we can judge from their appearance, they are 
composed of three principal parts, the head, the 
nebulous envelope, and the tail. 

THE HEADS OF COMETS. 

The head is comparatively small, seldom greater 
than our moon. In some comets it is altogether 
wanting. It usually appears less bright than even 
the planets, and is of a pale whitish colour. 

The following estimates have been made of the 
size of the heads of comets. 

The Comet of 1798, diameter of the head 33 miles. 
« " 1805 " " 36 " 

" " 1799 " " 462 " 

u a 1807 " " 666 " 

« " 1811 " " 3267 " 

THE NEBULOUS ENVELOPE. 

The nebulous envelope is the only universal 



282 COMETS. 

characteristic of comets. It has the appearance 
of a thin cloud of condensed vapour or smoke, 
surrounding the head of the comet when visible. 
It is gradually thickened towards the centre when 
no head is to be seen. Some comets which to the 
naked eye and in small telescopes have seemed to 
have a head, have, when greatly magnified in 
powerful telescopes, been wholly resolved into a 
cloudy-looking substance or nebulous envelope. 

THE TAIL. 

The tail of comets is usually the prolongation 
of the nebulous envelope in a direction from the 
sun. Sometimes the tail is wanting, and then the 
nebulous envelope is somewhat oval, or fan-shaped, 
with the densest portion not in the centre, but 
nearer the sun than the centre of the figure. The 
portion next the sun is in such cases rounded, the 
portion from the sun slightly elongated, and its 
outline not well defined. Sometimes the tail ex- 
tends to a great length, and it is often bent con- 
cavely on the side which is towards the point of 
the orbit which the comet is leaving. In such 
cases the concave border is better defined and 
smoother than the opposite or convex border. 

Some comets have had two tails. That of 
1823, for instance, had one tail extended towards 
the sun, the other from it. The comet of 1744 
had six tails, each about 4° in breadth, and 30° 
or 40° in length. Chladni noticed a rapid short- 



COMETS. 283 

ening and lengthening of the tail of the great 
comet of 1811, which amounted to several millions 
of miles in a second, a velocity of motion (if mo 
tion it was) far exceeding that of light. Many 
other astronomers have recorded similar appear- 
ances. They are not, however, considered to be 
well established. 

The comet which appeared 371 years before 
Christ, is said to have covered a third part of the 
visible heavens. That of 43 years before Christ, 
was so bright as to be seen in the day-time. It 
was supposed to be the ghost of Caesar, who had 
just been assassinated. Seneca mentions a comet 
in A. I). 60, which eclipsed the brightness of the 
rising sun. In 1402, two comets appeared; the 
one was seen in the day-time, in March; the other 
in June following, long before sunset. The tail 
of the comet of 1456 was 60° long. That of 1618, 
100°, so that its tail had not all risen when its 
head reached the middle of the heavens. The 
comet of 1680 was so great, that though its head 
set soon after the sun, its tail, 70° long, continued 
visible all night. The comet of 1689 had a tail 
68° long. That of 1744, which had six tails, had 
a head brighter than Venus, and could be seen 
with the naked eye an hour after midday. That 
of 1769 had a tail more than 90° in length. That 
of 1811 had a tail 23° long. The recent comet 
of 1843 had a tail 60° in length. 

These estimates are the angles under which the 
.tails were seen from the earth. The real lengths 



284 COMETS. 

of several comets' tails have been estimated as 

follows : 

Tail of Comet of 1680 123,000,000 miles. 

" " 1744 35,000,000 " 

" " 1769 48,000,000 " 

" " 1811 130,000,000 " 

" " 1843 130,000,000 " 

ORIGIN OF THE ENVELOPE AND TAIL OF COMETS. 

The tails of comets owe their origin to the ac- 
tion of the sun. They are usually directed from 
it. They increase as the comet approaches the 
perihelion, and decrease soon afterwards; and 
usually disappear before the comet has attained a 
distance of 200,000,000 of miles from it. 

The physical observations of Olbers on the comet of 1811, 
and of Bessel and Arrago on H alley's comet in 1835, have 
given us some insight into the nature of these bodies. Pro- 
fessor Norton, of Newark, Delaware, has recently, from his 
own researches, been led to conclusions similar to those of 
Olbers and Bessel. 

According to Arago, they shine by reflected light; and 
according to Olbers and Bessel, the nebulous envelope is 
formed by a repulsive force in the substances on the surface 
of the solid portion or head. It is quite probable that when 
at their greatest distance from the sun or aphelium, the heads, 
owing to the condensation of the volatile portions through 
extreme cold, become solid bodies like our earth. 

On nearer approach to the sun, the effect of its heat or 
light, or of both, is such as to volatilize the substances on its 
surface. These volatile substances do not resemble the gases 
or vapours on the earth's surface ; for they have no power of 
refracting the sun's rays. They may rather be compared to 
the particles of dust thrown off by electrical repulsion from 



COMETS. 285 

an excited conductor. In other words, the force which go- 
verns the distance of these volatile particles from each other, 
seems to be that of polarity, and not of elasticity. In many 
instances, stars have been seen through the densest portions 
of comets. This is explained by supposing that the force 
of polarity or repulsion is so great as to overcome that of 
cohesion of the particles, aud reduce the substances, which 
would otherwise be solid, to a state of thinness or subtility, 
exceeding that of the most volatile essences known to us. 
In this manner, the formation of the envelope has been sup- 
posed to be accounted for. The formation of the tails of 
comets is attributed to a second or solar polarity, acquired by 
the particles that have, by the first polarity or electrical repul- 
sion, been scattered about so as to form the envelope. As 
the comet approaches the sun from the frozen regions of 
space, the particles, besides being thrown off from the comet, 
are also repelled by the sun. Hence, in the direction from 
the comet and from the sun, they are moved by a double 
repulsive force, while, towards the sun, they feel only the 
difference of these forces. 

This explains the shape of the envelope and tail. The 
position of any particle of the envelope or tail at the time 
when we look at it, depends upon the time when it acquired 
its first polarity, so as to be thrown off from the head of the 
comet; the particular direction in which it was thrown; the 
degree of force in this direction ; the direction and velocity 
of its orbital motion at the time of separation from its cohe- 
sion with the head of the comet ; the time when it acquired 
its second or solar polarity, so as to be thrown off in a direc- 
tion from the sun; and finally upon the degree of repulsive 
force in that direction. 

All these circumstances vary every instant for the same 
comet, and are different for different comets. It is supposed 
that their various combinations will account for all the vari- 
ous shapes of comets. 

When the first or cometary polarity is very feeble, and the 



286 COMETS. 

second or solar polarity very powerful, the tail is long and 
narrow, as in 1668, 1689, and 1843. (See the drawing of the 
comet of 1843.) When, on the contrary, the comet's head is 
greater, and the cometary repulsion greater in comparison 
with the sun's repulsion, the tail is broader, and the portion 
of the envelope towards the sun extends farther from the 
head, leaving an almost vacant space between the border of 
the envelope and the head. The shape of the nebulous enve- 
lope and tail, is usually that of a hollow hyperboloid. (See 
the drawing of the comets of 1811 and 1819.) 

WASTE OF THE SUBSTANCE OF COMETS BY DISSIPATION 
IN SPACE. 

The particles that form the tails of comets, and the extreme 
portion of the envelope, having passed beyond the sphere of 
active attraction of the head, can never return, but wander in 
space, till they become too thin to be seen, and are lost to 
our view and our knowledge. 

Comets that return often to their perihelion seem to lose 
those particles that are capable of secondary or solar polariza- 
tion, and have no tails. Such is the case with Encke's and 
Gambart's comets. Halley's comet in its recent returns is 
far less terrific than under similar circumstances in ancient 
times. 

It is impossible to conjecture what becomes of the particles 
of comets thus thrown off and dispersed through space. If 
the solar repulsion continues, they must move off in hyper- 
bolas to the confines of the system, perhaps to join with 
other nebulae, other systems, or other planets, to revolve round 
other suns in a more friendly relation. 

POPULAR SUPERSTITIONS RESPECTING COMETS. 

The appearance of comets in ancient times was 
always a source of alarm. They were supposed, 
without just foundation, to be the forerunners of 
the direst calamities, wars, famine, pestilence, 



Great Comet of 1811. 




Great Comet of 1819. 



COMETS. 287 

deaths of great men, &c. So great was the alarm 
in Christendom in 1456, during the appearance of 
Halley's Comet, that Pope Calixtus, believing it 
to be the instrument of Divine wrath, ordered 
prayers to be offered up in every town, and the 
bells to be tolled at noon of each day, to warn the 
people to supplicate the mercy of heaven. He at 
the same time excommunicated both the comet, 
and the Turks, whose armies had lately proved 
victorious against the Christians, and established 
the custom, which still exists in Catholic coun- 
tries, of ringing the church-bells at noon. 

Comets have also been supposed to produce irre- 
gularities in the seasons. When we reflect, that 
probably no season passes by without our having 
at least one comet as near to us as Jupiter, we 
find no just grounds for attributing to this source 
any of the calamities with which mankind are 
occasionally afflicted. 

Another source of apprehension with regard to 
comets arises from the possibility of their striking 
our earth. It is quite probable that even in the 
historical period the earth has been enveloped in 
the tail of a comet. It is not likely that the effect 
would be sensible at the time. The actual shock 
of the head of a comet against the earth is ex- 
tremely improbable. It is not likely to happen 
once in a million of years. 

If such a shock should occur, the consequences 
might perhaps be very trivial. It is quite possible 
that many of the comets are not heavier than a 



288 COMETS. 

single mountain on the surface of the earth. It is 
well known that the size of mountains on the 
earth is illustrated by comparing them to particles 
of dust on a common globe. 

The comet of 1770, which approached so near 
to Jupiter as to have its orbit and period com- 
pletely changed, produced no sensible effect on the 
satellites of that planet. It is by no means un- 
common for one of the planets to alter a comet's 
period round the sun by more than a month, while 
at the same time that of the planet itself is never 
changed by the comet a single second. 

THE ELEMENTS OF THE ORBITS OF COMETS. 

In describing the orbits of the planets, six ele- 
ments are usually mentioned. This cannot be 
done with the greater part of the comets: the 
longer axis and period are unknown. The remain- 
ing five elements are the same with comets as 
with planets. 

The average of all the inclinations of the planes 
in which the comets now on record have been 
found to move is about 90°, a wonderful instance 
this of the goodness of Providence in causing 
their motions to be performed in the manner least 
likely to come in contact with the earth and the 
other planets ! 

The shape of their orbits is also usually that 
of very flattened ellipses or parabolas, so that 
they approach the sun and again quickly depart 
from the limits of the planetary system, and 



COMETS. 289 

remain for years, or centuries, or ages, beyond the 
limit of our vision, even with the best telescopes, 
another instance of the protecting care of an all- 
pervading Providence ! 

The paths of most of the comets may be well represented 
by assigning to them a parabola for their orbit. In fact the 
small portion of the orbit in which we see them near their 
perihelion, is almost the same in a parabola as in an ellipse. 
Yet it is probable that they all move in ellipses, and have 
their stated periods round the sun, embracing all varieties, 
from a few years to many centuries. Among a million of 
possible combinations of original projectile force, direction, 
and position with respect to the sun, with which a comet may 
have been endowed at creation, there is only one that would 
produce a circle or a parabola for its orbit. The remaining 
combinations would produce ellipses or hyperbolas. The lat- 
ter curve is, at present, extremely improbable ; for if any 
comets have moved in hyperbolas, they can never have made 
but one visit to our system, and most of them must ere this 
have finished their revolution in this system, and be far on 
their way to another. Still astronomers are occasionally led 
in their investigations to hyperbolas for the orbits of comets. 
This circumstance occurred several times in the researches 
of the celebrated French astronomer Burckhardt. Such irre- 
gularities are usually ascribed to the imperfection of our ob- 
servations of the places of the centre of the comet's head. 
Our estimate is liable to be biassed by its eccentric position 
in the nebulous envelope. 

It is possible that a comet may approach from an immense 
distance towards the sun in an elliptic orbit, while its head 
remains solid. If on its nearer approach to the sun its enve- 
lope is formed by the particles thrown off from the head, little 
change will be produced in its orbit. But when the solar 
repulsion of a portion of the envelope is induced, the effect of 
this repulsion on the particles not yet beyond the sphere of 



290 COMETS. 



active attraction of the comet, must tend to increase the ec- 
centricity of the orbit. In comets like that of 1843, where 
the solar repulsion is very powerful, and where the head is 
almost wholly resolved into nebulous envelope, the effect of 
the sun's repulsion may be sufficient when the comet is near 
the sun, and the ellipse is very eccentric, to change the in- 
stantaneous orbit into a portion of an hyperbola ; and again 
the comet may, on departure to a sufficient distance from the 
sun for the solar repulsion to cease or be much weakened, 
resume its elliptic orbit, and having attained its greatest dis- 
tance from the sun, again return to experience similar changes 
and modifications. In the case of the comet of 1843, the 
nicest observations which could be made with the choice 
instruments at the High School Observatory for a period of 
20 days, lead, on sound principles of computation, to an hy- 
perbola for its orbit. This result may have been owing to 
the imperfection of the observations, or possibly to the cir- 
cumstance just mentioned. 

PERIODICAL COMETS. 

Although it is probable that all the comets 
move in ellipses so eccentric as nearly to resemble 
a parabola, yet few of their periods have been 
determined. Some revolve in orbits of several 
thousand years. Perhaps the average period is 
not far below one thousand. The elements of all 
the comets whose places have been observed, are 
computed and preserved in catalogues in order 
to detect their future returns. The list of comets 
thus registered, amounts to about 150. When- 
ever a comet appears whose elements are the 
same as those of any of the comets in the cata- 
logue, it is presumed to be identical, and the in- 






COMETS. 291 

terval since the recorded appearance is considered 
as constituting one or more periods. 

HALL EY'S COME T. 

This comet revolves round the sun from east to 
west in 75^ years, in an elliptic orbit inclined 
17° 44' to the ecliptic. Its least distance is 
56,000,000 and its greatest 1,710,000,000 of miles. 
Its eccentricity is 0.97. It bears the name of 
Halley, who discovered its period. In its perihe- 
lion, it approaches nearer the sun than Venus, 
and in its aphelion it departs to the distance of 
Uranus. It remains within the orbit of the earth 
at its perihelion 2\ months ; but its orbit is so 
situated that it never approaches within several 
millions of miles of our planet. 

SUPPOSED APPEARANCES OF HALLEY'S COMET. 

The earliest recorded appearance of Halley's 
comet is supposed to have been 138 years B. C. 
This would be the 26th period prior to its recent 
visit in 1835. After an omission in the chronicles 
for five periods, we find mention of a comet in 
A. D. 323, at the time of the famous Council of 
Nice, in the reign of Constantine. Its next re- 
turn, in 399, occurred during the session of the 
Council of Alexandria, the year in which the 
Vandals overran southern Europe. Its appear- 
ance is described as being " exceedingly terrific, 
of great magnitude, and with its tail extending 



292 COMETS. 

down to the earth." After two periods, it again 
appeared in 547, the year in which Rome was 
plundered by Totilas. 

Its fifth recorded appearance was in 930, after 
an interval of four revolutions. At this time it 
was considered the forerunner of the death of 
Henry the Fowler, and the subjugation of Hun- 
gary. Its sixth and seventh appearances were in 
1005 and 1080, the latter being the year of the 
death of the Emperor Alexius Comnenus. The 
eighth appearance was in 1155, during the Coun- 
cil of Soisson. The ninth is mentioned in 1231, in 
the Chinese Annals. The tenth was in 1305 : its 
appearance was then the cause of general alarm, 
and was followed by a severe winter, and by a 
plague which raged in Europe for several years. 
It is supposed to be one of the two comets which 
appeared in 1379 and 1380. These eleven ap- 
pearances are inferred chiefly from a coincidence 
in dates. For want of astronomical observations, 
they will always be subject to doubt. 

CERTAIN APPEARANCES OF HALLEY's COMET. 

The first certain appearance was in 1456: its 
tail was 60 degrees in length, and broad like a 
peacock's tail, as has been already noticed. Its 
next undoubted appearance was in J531. The 
third was in the time of Kepler, in 1607. It tra- 
versed the northern constellation as in 1835. Its 
fourth appearance was in 1682, in the time of 



COMETS. 293 

Newton, when it was regarded as a friendly visi- 
ter, and not as the harbinger of Divine wrath. 

Its period was soon after ascertained by Halley, 
who computed the elements of all the comets on 
record, and found that three of them, viz. those 
of the great comets of 1456, 1531, and 1607, had 
similar elements to those of the comet of 1682. 
Accordingly, he assigned to it a period of 76 
years, and predicted its return in 1758. In reali- 
ty, it returned in 1759, having been retarded 100 
days by Saturn, and 518 by Jupiter, according to 
the subsequent predictions of Clairaut. In 1835, 
its return was predicted by eminent astronomers 
early in November. It actually came to its peri- 
helion on the 16th. The period of this comet is 
now well established, and its return early in the 
next century will doubtless be foretold within a 
single day. 

OLB E RS 5 S COMET. 

This comet was discovered by Olbers in 1815. 
It revolves round the sun in 75 years. Its orbit 
is inclined 44° to the ecliptic. Its least distance 
is 116,000,000 and its greatest 1,557,000,000 of 
miles; its eccentricity being 0.93. Its orbit is so 
situated that it can never come very near the 
earth. It will return to its perihelion about the 
9th of February, 1887. It is a small faint comet 
and has probably escaped notice in its former 
returns. 
20 



294 COMETS. 

encke's comet. 

Encke's comet, or the comet of short period, re- 
volves round the sun in 1210 days, in an orbit 
inclined 13° 22' to the ecliptic. Its eccentricity- 
is 0.854. Its least distance from the sun is 
31,000,000 of miles, being within the orbit of 
Mercury. Its greatest distance is 390,000,000 of 
miles, being between the orbits of the Asteroids 
and Jupiter. 

It was discovered by Pons in 1819, but its pe- 
riod was first ascertained by Professor Encke. It 
had been seen by Messier and Mechan in 1786, 
by Miss Caroline Herschel in 1795, and by all the 
astronomers in Europe in 1805. Its returns in 
1825, 1828, 1832, 1835, 1838, 1842, have all been 
observed, and its place is now computed in ad- 
vance almost as well as that of the planets or 
asteroids. In 1838, it was visible to the naked 
eye as a nebulous star of the 4th magnitude. It 
has no tail, though its nebulosity is always mani- 
fest, and in 1838 extended through several min- 
utes. The densest portion of the nebulosity is 
always eccentric in its position in the envelope, 
being nearer to the sun than the centre, and hav- 
ing the portion from the sun somewhat fan-shaped. 

The perihelion point of the orbit of Encke's comet falling 
just within that of Mercury, and being only 3° from its de- 
scending node, if it passes that point when Mercury is in the 
sign of the Virgin, they must approach near each other. 
This combination occurred in 1838, and furnished Encke the 



COMETS. 295 

means of determining the mass of Mercury, more precisely 
than it was known before. 

This comet is found to encounter a slight re- 
sisting medium in its path for a few months before 
and after the perihelion passage. This takes 
place while it is within the orbit of Venus. 

As this resistance tends to weaken the tangential or cen- 
trifugal force of the comet, the attractive or central force of 
the sun gains continually on it, increases its angular motion, 
shortens its period, and diminishes its mean distance. 

This quickening of the angular motion is such, that the 
comet advances in each revolution one minute of space 
farther in its orbit, than it would do by Kepler's Laws if it 
moved in a perfect void. This advance brings the comet 
back to its perihelion, each time, one hour and twenty minutes 
sooner than before. The accumulation of these advances 
since 1785, in 17 revolutions, to 1842, amounts to about 17^ 
days, a quantity too great to be reasonably ascribed to any 
other known cause, for the want of which the theory of a 
resisting medium in the planetary spaces between Venus and 
the Sun, is resorted to as a matter of necessity. 

Bessel has shown that there are many other causes known 
to exist, which are capable of producing an acceleration in 
the mean motion of Encke's comet ; but Encke remarks with 
reason, that each of the causes enumerated by Bessel, would 
produce other effects which we do not notice in the case of 
the comet of short period. The grounds for adopting the 
Enckian theory of a resisting medium, are similar to those 
in favour of the Copernican system, viz : that it explains all 
the observed facts, and that no other hypothesis will. 

Encke assumes that the density of this medium increases 
as the square of the distance from the sun diminishes, and 
that it resists the comet with a force increasing as the square 
of the comet's orbital velocity increases. It is not known of 



296 COMETS. 

what substance this resisting medium is composed, or by 
what means it maintains its distance from the sun. Some 
have supposed it to be the zodiacal light, or nebulosity which 
surrounds the sun ; others have supposed it to be the source 
of the periodical meteors, each of which has been considered 
an independent asteroid, revolving round the sun in its own 
orbit, the average number of them in any portion of space 
increasing, by the same law as the resistance increases. 

Encke's comet will return to its perihelion early in August, 
1845, and late in November, 1848. In 1845 the visit will be 
under unfavourable circumstances for observation. 

gambart's comet. 
This was discovered on the 27th of February, 
1826, by M. Biela ; but M. Gambart, of Mar- 
seilles, first ascertained that its elements were the 
same as those of the comets of 1772 and 1806, 
and hence that its period was 2460 days, or about 
6f years. It is inclined 13° to the ecliptic. Its 
eccentricity is 0.75 ; its least distance is 86, its 
greatest distance 586 millions of miles, being situ- 
ated between the orbits of Venus and Saturn. 

It is possible that this comet, as well as Halley's, experi- 
ences the effect of the resisting medium. Halley's comet 
only approaches to the orbit of Venus, and Gambart's to that 
of the earth, distances at which Encke is unable to detect 
any resistance to the motion of his comet. Even if this me- 
dium extends beyond the earth, the elements of Halley's and 
Gambart's comets are not known with sufficient precision to 
detect such a resistance. 

Gambart's comet was seen in its return to its 
perihelion in 1826, but not in 1839, verifying, in 
this respect, the predictions of Santini, who found 
from a computation of its ephemeris that in 1839 



COMETS. 297 

it would always be too nearly in the line joining 
the earth and sun, and too remote from the earth 
to admit of being seen. 

Santini has announced its return to its perihe- 
lion, February 11th, 1846, under favourable cir- 
cumstances. It is expected to be visible for a 
month or two before and after that date. 

COMETS SUPPOSED TO BE PERIODICAL. 

Besides these comets of established period, there 
are several others supposed to be identical with 
former visitors. 

The comets of 975, 1264, and 1556, are found 
to have similar elements, as far as we can judge 
from the imperfect accounts derived from the an- 
cient chronicles. If they are the same, the period 
is about 291 or 292 years, and the comet should, 
in this case, return in 1847 or 1848. This is, 
however, quite doubtful. 

The comet of 1680 was formerly supposed to 
have a period of 575 years. A very careful dis- 
cussion of all the ancient observations, by Encke, 
is considered as conclusive against this supposition. 

The comet of 1770 was found, by Lexell, to 
have a period of 5j years, yet it has never been 
seen since. La Place found that the action of Ju- 
piter previous to the year 1770 had so completely 
changed the form of the orbit of this comet as to 
bring it into view in 1770, though it had been in- 
visible before. After 1770, Jupiter produced a 
contrary effect, and caused it to revolve in an orbit 



298 COMETS. 

having its perihelion distance beyond Ceres, so 
that, perhaps, it will never again be visible. 

The great comet of 1843, which is fresh in our 
recollections, strongly resembled in its appearance 
those of 1668 and 1689. It is also found that one 
set of elements, with a period of 21 J years, will 
represent the paths in the heavens of the comets 
of these three dates. If they are the same, it will 
return again about the beginning of the year 1865. 

Mr. Clausen of the Dorpat Observatory, Mr, 
Capocci of Naples, and the astronomers of the 
High-School Observatory, in Philadelphia, each, 
without the knowledge of the others, have ex- 
pressed themselves in favour of this short period. 
Capocci has even thought it possible that it may 
return three times in that term. 

Mr. Nicolai, of the Manheim Observatory, has 
examined the effect of a shortening of its period 
upon its elements for 1843, and concludes that it 
is perfectly consistent w 7 ith all that is known of 
its path in the heavens on that occasion. 

THE THIRD COMET OF 1843. 

This comet was discovered on the 25th of No- 
vember, 1843, by M. H. Faye, of the Paris Ob- 
servatory. It was re-discovered in this country 
on the 27th of December, by Mr. J. S. Hubbard, 
at the New-Haven Observatory. The parabolic 
elements of several astronomers being found un- 
satisfactory, M. Goldschmidt, of Gottingen, at the 
request of Gauss, computed, in December last, an 
orbit on the method of the latter, and found a 




Great Comet of 1843. 



COMETS. 299 

period of 6§ years. M. Faye, in January, com- 
puted an orbit on the same method, and found a 
period of 7} years. The astronomers of the Phi- 
ladelphia High-School Observatory have computed 
an orbit on a similar plan, from a series of obser- 
vations, including an interval of 61 days, and 
found a period of 6£ years. The motion is direct, 
the inclination to the ecliptic is 11° 6'. The ec- 
centricity is 0.52. The least distance is 162, and 
the greatest is 522 millions of miles from the sun. 
This comet can never approach within 60 millions of miles 
of the earth ; but its aphelion distance being a little greater 
than that of Jupiter, and occurring near the ascending node, 
when this event takes place while Jupiter is about entering 
the sign of the Scorpion, they may approach very near each 
other and remain so for the greater part of a year. This 
event occurred in the year 1840, at which time Jupiter's 
attraction for this comet was about a tenth part of the sun's, 
and must have produced a considerable alteration of its orbit. 

This heavenly body seems to form a connecting 
link between the asteroids and the other comets. 
Hitherto there was a well-marked distinction be- 
tween planets and comets. The eccentricity of 
the former was below one quarter, that of the lat- 
ter above three quarters. This body, with an 
eccentricity of one half, holds a medium rank, 
and removes one of the most distinctive features. 
In the degree of nebulosity of the surfaces of 
planets and comets there is also a gradation. 
Mars is more nebulous than the other old planets 
except, perhaps, the earth. Ceres is surrounded 
by a still greater nebulosity. Next in degree of 



300 COMETS. 

nebulosity are this comet and those of Encke and 
Gambart. 

The position of its orbit in the heavens is quite 
unstable ; perhaps its present short period is owing 
to the action of Jupiter in 1839 and 1840. On 
some future occasion Jupiter may possibly cause 
it to move in such an orbit as to become invisible. 
Its fate would then resemble that of LexePs 
comet. 



ECLIPSES OF THE MOON. 301 

SEC. 23. 

ECLIPSES OF THE MOON. 

Since the earth and the moon are opaque bodies, 
receiving their light from the sun, and being both 
much smaller than the sun, they must always 
carry with them a shadow of a conical form, the 
axis of which is a line drawn from the centre of 
the sun through the centre of the earth or moon. 
When the moon passes through the shadow of the 
earth it is wholly or partially deprived of the 
sun's light by the interposition of the earth : this 
phenomenon is called an eclipse of the moon or a 
lunar eclipse ; it can only happen w T hen the moon 
is in opposition, or at the time of full moon : if 
the moon always moved in the plane of the eclip- 
tic, it would pass through the earth's shadow and 
be eclipsed every full moon. But, as has been 
already stated, the lunar orbit is inclined to the 
plane of the ecliptic, and only coincides with it 
in two points, called the nodes ; and she will be 
eclipsed at the full moon only when that occurs 
near one of the nodes, at other times she will pass 
either above or below the shadow of the earth at 
the time of her full phase. 

When the moon is at such a distance from the 
node, at the time of opposition, as to be only in 
part involved in the shadow, the eclipse is said to 
be partial. If the whole disc of the moon is ob- 
scured by the shadow, it is called a total eclipse. 



302 ECLIPSES OF THE MOON. 

And when it is exactly in its node at the time of 
opposition, the centres of the sun, earth and moon 
all lie in the same straight line, and the moon's 
centre passes through the centre of the shadow; 
it is then said to be centrally eclipsed. 

The conical shadow of the earth terminates in 
a point about 3j times the distance of the moon 
from the earth. The breadth of the shadow at 
the point where the moon passes through it is, on 
the average, about 2§ times the moon's diameter. 

The apparent diameter of the disc of the moon 
is divided into 12 equal parts, called digits. The 
greatest eclipse of the moon may amount to 22 
digits ; this is called the quantity of the eclipse. 

The duration of a lunar eclipse depends partly 
upon its quantity, and partly upon the velocity 
of the moon's motion across the shadow, which is 
the same as her motion from the sun. This mo- 
tion is swiftest when the moon is in her perigee ; 
and the duration of a central eclipse will then be 
shortest, though the moon's diameter and that of 
the shadow, at the place where the moon passes 
through it, are greatest. The longest duration 
of a partial eclipse is about 2 hours 18 minutes, 
and that of a total eclipse 4 hours 38 minutes. 

In Fig. 1, on the following plate, let S be the 
centre of the sun, E that of the earth, and a, b 
and c, the centre of the moon in its orbit, a por- 
tion of which is represented by the arc m, n. The 
space g 9 T, h, included between the tangent lines 
H, h, T, and G, g, T, will represent the shadow 




(303) T 



304 ECLIPSES OF THE MOON. 

or umbra, and E, T, the axis of the shadow. The 
entire disc of the sun will be hidden by the earth 
from all points within that space. The space be- 
hind the earth, included between the tangent lines 
H, g, n, and G, h, m, which touch the sun and 
earth on opposite sides, is called the penumbra ; 
it is a frustrum of a cone, only a section of which 
is represented in the figure. From any point 
within this frustrum, but not in the shadow, a 
part of the sun's disc only can be seen. 

When the moon arrives at the point m, she be- 
gins to lose sight of the sun, and in passing from 
m to c the visible portion of the sun's disc dimin- 
ishes to a very small segment, near the point H ; 
the moon, as seen from the earth, grows more and 
more faint until she reaches the shadow, at which 
time the eclipse begins upon the eastern side of 
the moon. The eclipse ends when the moon 
reaches the position a 9 where the western limb of 
the moon just touches the shadow. 

It is impossible to determine by observation the 
precise instant when a lunar eclipse begins or ends, 
in consequence of the shade of the penumbra 
blending into that of the umbra in such a manner 
as to render it difficult to distinguish the line of 
separation. Eclipses of the moon are, therefore, 
of very little value for astronomical or geogra- 
phical purposes. Every eclipse of the moon is 
visible at the same instant of absolute time, to all 
parts of the earth above whose horizon the moon 
is at that time situated. 



ECLIPSES OF THE SUN. 305 

ECLIPSES OF THE SUN. 

The moon, when in conjunction, if near one of 
her nodes, is interposed between the earth and 
the sun, and consequently hides the sun, either 
wholly or in part, from us : this phenomenon is 
called an eclipse of the sun or a solar eclipse. 

These eclipses can only occur at the time of 
new moon, and not then, unless the moon is at or 
near one of her nodes, owing to the inclination of 
her orbit to the plane of the ecliptic. 

In Fig. 2, S, M and E represent the centres of 
the Sun, Moon and Earth ; the dark space between 
the lines a m and c m\ represents a section of the 
moon's conical shadow which w T ould terminate at 
b if it were not cut off by the surface of the earth 
at m m'. This shadow is surrounded, as is that 
of the earth, by a penumbra, of the form of a 
frustrum of a cone, represented by the lighter 
space between the lines a n and c n'. 

As the moon moves in her orbit from A towards 
C, her penumbra moves over the earth's surface 
from west to east, passing in succession over dif- 
ferent parts. At all places on the line traversed 
by the axis or centre of the shadow, the sun is 
centrally eclipsed ; and at all places near this line 
over which the shadow passes the eclipse is total; 
and at all places traversed by the penumbra, but 
not by the shadow, only a part of the sun's disc 
is obscured by the moon, and the eclipse is partial. 
The magnitude of the partial eclipse is in propor- 



306 ECLIPSES OF THE SUN. 

tion to the nearness of the place to the shadow. 
At the points n or n' the moon appears only to 
touch the disc of the sun. 

If the moon, at the time the sun is centrally 
eclipsed, is at such a distance from the earth that 
its shadow does not reach the surface of the latter, 
at all places on the line traversed by the axis of 
the cone, the edge of the sun appears as a bright 
ring surrounding the moon. This phenomenon is 
termed an annular eclipse. 

If at the time of conjunction the moon is so far 
from her node that her shadow does not touch the 
earth, the sun is not totally eclipsed at any part 
of the earth's surface ; but those places passed 
over by the penumbra experience a partial eclipse. 

The greatest breadth of the path of the shadow 
of the moon over the earth's surface is about 170 
miles. This occurs when the moon is in its peri- 
gee and the earth in its aphelion at the time of 
conjunction. When the moon is in its apogee and 
the earth in its perihelion at the time of conjunc- 
tion, the eclipse, if there be one, is annular; the 
apparent diameter of the moon is then much less 
than that of the sun, and the breadth of the annu- 
lus or ring is the greatest possible. The greatest 
breadth of the path traversed by the moon's pe- 
numbra when it falls perpendicularly on the sur- 
face, is about 4830 miles. An eclipse of the sun 
is therefore visible only to a small portion of the 
inhabitants of the earth, who see it differently ac- 
cording to their different situations upon its sur- 



ECLIPSES OF THE SUN. 307 

face. The greatest breadth of that part of its 
surface at which an eclipse can be annular, is 
about 200 miles. 

The longest possible time that a solar eclipse 
can continue total, at any place, is 8 minutes; 
and the longest time that an eclipse can continue 
annular, is 12 minutes. 

When the moon at the time of conjunction is 
19f° distant from her nearest node, there can be 
no eclipse ; if the distance is less than 13^°, there 
must be an eclipse for some part of the earth ; and 
if its distance is between these limits, a further 
calculation is necessary to determine whether an 
eclipse will happen or not. For eclipses of the 
moon, these limits are much more narrow. An 
eclipse of the moon can never happen when she 
is, at the time of opposition, more than 13^° from 
her nearest node, and an eclipse is certain only 
when she is within 7f° of her node : between these 
limits the moon will sometimes be eclipsed, and at 
other times not. 

There can never be more than seven, nor less 
than two eclipses in a year. When there are but 
two, both are of the sun ; when there are seven, 
five of them are of the sun and two of the moon. 

In a series of 223 lunar months, the eclipses 
occur nearly in the same order and magnitude. 
223 synodic revolutions of the moon, and 19 syno- 
dic revolutions of her line of nodes, differ from 
each other only by about 0.46 of a day, so that at the 
end of this period the earth, the moon, the sun, and 



308 TIDES. 

the moon's nodes, are nearly in the same relative 
positions as at the beginning of it. This period 
is 18 Julian years and 11 days, and in general 
there will be in this space of time 70 eclipses, of 
which 29 are of the moon, and 41 are of the sun. 

This period was known to the Chaldean astro- 
nomers, by whom it was called the Saros. It was 
used by them in predicting eclipses. 



SEC. 24. 

TIDES. 

The ocean, which covers more than one-half of 
our globe, is in continual motion, rising and fall- 
ing alternately without intermission. This eleva- 
tion and depression is denominated the tide, and 
is occasioned by the influence of the sun and 
moon, more particularly of the latter. The rising 
of the tide is called flood, and its falling ebb tide. 
When the water has reached its greatest height, 
it is said to be high tide; and when after ebbing 
it has reached its least elevation, it is said to be 
low tide. 

The surface of the ocean rises and falls twice 
in the course of a lunar day, or 24h. 50m. 48s. of 
mean solar time. The average interval between 
two successive high or low tides, is 12h. 25m. 24s. 

There are also two kinds of tides, each of which 
occur twice in a lunar month : the spring tides 



TIDES. 309 

happen about the time of new and full moon, and 
are higher than the ordinary tides ; the neap tides 
occur about the time of the first and last quarter 
of the moon, at which time the surface of the 
ocean at high tide is less elevated than at other 
times. The tides are also higher than usual about 
the vernal and autumnal equinoxes, and highest 
at the latter period. 

The sea is observed to flow from the east to- 
wards the west for about six hours ; then, after an 
apparent rest of about a quarter of an hour, it 
begins to ebb, or retire, for about the same time. 
The rivers, which had their motion reversed, re- 
sume their natural course; and, after another 
seeming pause of a quarter of an hour, the sea, 
which has now fallen to its lowest pitch, begins 
to rise again. Thus it continues to rise and fall 
alternately throughout the year ; but w T ith a differ- 
ence in time of about 50 minutes every day, the 
same time that the moon varies in coming to the 
meridian of any given place. 

The retardation in the time of high water, how- 
ever, varies with the phases of the moon: it is 
least near the syzygies, when the tides are at 
their maximum, and greatest near the quadra- 
tures, when the tides are at their minimum. The 
variation in the distances of the sun and moon 
from the earth, and also their declination, have 
an effect on the retardation of the tides. When 
the moon has north declination, the tides are 
higher in northern latitudes when she passes the 
21 



310 TIDES. 

meridian above the horizon, than when she passes 
below it : but when she has southern declination, 
the reverse of this takes place. 

If the earih were at rest, and there were no 
influence from either sun or moon, the waters in 
the ocean would be truly spherical. On the other 
hand, if the earth and moon were without motion, 
and the earth covered all over with water, the 
attraction of the moon would raise the water in a 
heap in that part of the ocean to which the moon 
was vertical; and there probably it wouta always 
continue. But by the rotation of the earth upon 
its axis, each part of its surface to which the 
moon is vertical, is presented to the action of the 
moon ; and thus are produced two floods and two 
ebbs in every rotation. 

The particles of water under the moon are more attracted 
than the centre of gravity of the earth, in the inverse ratio of 
the square of the distances ; hence they have a tendency to 
leave the earth, but are retained by their gravitation, which 
is diminished by this tendency. On the contrary, the moon 
attracts the centre of the earth more powerfully than she at- 
tracts the particles of water in the hemisphere opposite to 
her ; so that the earth has a tendency to leave the waters, but 
is retained by gravitation, which is again diminished by this 
tendency. Thus the waters immediately under the moon 
are drawn from the earth at the same time that the earth is 
drawn from those which are diametrically opposite to her; in 
both instances producing an elevation of the ocean of nearly 
the same amount; for the diminution of the gravitation of the 
particles in each position is almost the same, on account of 
the distance of the moon being great in comparison with the 
earth's radius. 



TIDES. 



311 



The distance of the moon from the centre of the earth is 60 
times the radius of the latter; and hence her distance from the 
surface of the ocean immediately under her is f|< of her dis- 
tance from the centre. Now, since attraction varies inversely 
as the square of the distance, the moon's attraction for the 
particles of water under her is § fjf- of her attraction for the 
centre of the earth, or the former is about 3^ greater than the 
latter; and on the contrary her attraction for the waters on 
the opposite side of the earth is nearly 3^ less than her at- 
traction for the centre. Were the earth entirely covered by 
the sea, the water thus attracted by the moon would assume 
the form of an oblong spheroid, whose greater axis would 
point towards the moon, since the columns of water under the 
moon and in the direction diametrically opposite to her, are 
rendered lighter in consequence of the diminution of their 
gravitation ; and in order to preserve the equilibrium, the axes 
90° distant would be shortened. The elevation, on account 
of the smaller space to which it is confined, is twice as great 
as the depression, because the contents of the spheroid al- 
ways remain the same. The effects of the sun's attraction 
are in all respects similar to those of the moon's, though less 
in degree, on account of its distance : he therefore only modi- 
fies the form of this spheroid a little. 

If the waters were capable of assuming the form of equili- 
brium instantaneously — that is, the form of the spheroid — its 
summit would always point to the moon, notwithstanding the 
earth's rotation ; but on account of their resistance, the rapid 
motion produced in them by rotation prevents them from as- 
suming at every instant the form which the equilibrium of 
the forces acting on theiru requires. Hence, on account of 
the inertia of the waters, if the tides be considered relatively 
to the whole earth, and open sea, there is a meridian about 
30° eastward of the moon, where it is always high water, 
both in the hemisphere where the moon is, and in that which 
is opposite. On the west side of this circle the tide is flow- 
ing, on the east side it is ebbing, and on every part of the 



312 TIDES. 

meridian 90° distant, it is low water. These tides must ne- 
cessarily happen twice in a day, since the rotation of the 
earth brings the same point twice under the meridian of the 
moon in that time ; once under the superior, and once under 
the inferior, meridian. 

The mean force of the moon to move the waters 
of the ocean is to that of the sun as 5 to 2, nearly. 
Therefore, if the action of the sun alone produce 
a tide of two feet, that of the moon will be five 
feet. Hence, when the sun and moon act jointly 
on the tides, which is the case at the change and 
full of the moon, they are stronger and run higher 
than at other times, and constitute the spring 
tides: but when the sun and moon are 90 degrees 
apart, their attractive powers are opposed, and 
the tides are consequently weaker and lower ; and 
these are the neap tides. 

It has been already stated, that when the moon 
is in her quarter, the tides are at the lowest, be- 
cause the influences of the sun and moon counter- 
act each other ; that is, they act in different direc- 
tions ; the attraction of the one raising the waters, 
while that of the other depresses them. The 
moon of herself would raise the waters five parts 
under her; but the sun, being then in a line with 
low water, would keep th$ tide from falling so 
low there by two parts, and consequently from 
rising so high under and opposite to the moon, so 
that the height of the waters in the latter places 
would be reduced to three parts. 

The tides are known to rise higher at some 



TIDES. 



313 



seasons than others; which may be accounted for 
on the principle of the moon moving round the 
earth in an elliptic orbit, which brings her nearer 
to the earth at one time than at another. When 
she is nearest, her attraction is the strongest, and 
consequently it raises the tides most ; and when 
she is farthest from the earth, the tides are low- 
est, because her attraction is the least. 

But for what has been said, it might be sup- 
posed that the tides are highest when the moon is 
on the meridian, or due north or south. But how- 
ever just the theory, this is not the case experi- 
mentally. In open seas, as remarked above, where 
the water flows freely, the moon has generally 
passed the meridian about two hours when it is 
high water. This is owing to the impetus given 
to the waters : for even were the moon's attrac- 
tions to cease upon her arrival at the meridian, 
the motion of ascent given to the water would 
make it continue to rise for some time after ; and 
much more must it do so when the attraction is 
not withdrawn, but only diminished; as a little 
impulse given to a moving ball will cause it to 
move still farther than it otherwise would have 
done. 

The tides also answer not always to the same 
distance of the moon from the meridian, at the 
same place ; but are variously affected by the ac- 
tion of the sun, which brings them on sooner when 
the moon is in her first and third quarters, and 
keeps them back later when she is in her second 



314 TIDES. 

and fourth. In the former case, the tide raised 
by the sun alone would be earlier than the tide 
raised by the moon ; and in the latter case, later. 

The greatest spring tide will happen when the 
moon is in perigee, if other things be the same ; 
and the succeeding spring tide, when the moon is 
in apogee, will be the least. But as the effect of 
a luminary is greater the nearer it approaches the 
plane of the equator, and as the earth is nearer 
the sun in winter than in summer, and still nearer 
in February and October than in March and Sep- 
tember, the greatest tides happen not till some 
time after the autumnal equinox, and return a 
little before the vernal. 

Although the highest tides are produced by the 
conjunction and opposition of the sun and moon, 
their effects are not immediate ; but, from the con- 
tinuation of motion, are greatest and least some 
time after their forces have ceased to co-operate. 
Hence the highest spring tides generally occur 36 
hours after the new and full moons, and the low- 
est neap tides 36 hours after the first and third 
quadratures. 

In places remote from the equator, the two im- 
mediately succeeding tides are unequal whenever 
the moon declines from the equator; the evening 
tides in summer exceeding the morning tides, and 
the contrary in winter. For if the greatest eleva- 
tion immediately under the moon point to one 
side of the equator, the opposite greatest elevation 
will point as much to the other side ; and those 



TIDES. 315 

places which are on the same side of the equator 
with the luminary approach nearer to the great- 
est elevation when she is above the horizon, than 
to the greatest opposite elevation when she is 
below it. This inequality is greatest when the 
sun and moon have the same declination, and also 
in places most remote from the equator. The 
nearer the place approaches the pole, the farther 
is it removed from the greatest elevation on the 
opposite side of the equator; and the less tide, 
continually diminishing as the place approaches 
the pole, is at length lost altogether, so that only 
one tide occurs in the day. 

In open seas, the tides do not rise to very great 
heights, compared with what they do in wide- 
mouthed rivers, opening in the direction of the 
stream of the tide ; for. in channels growing gra- 
dually narrower, the water is accumulated by the 
contracting banks. The general elevation in the 
open sea is about 11 feet for spring tides, and 7 
feet for neap tides : yet at London the spring tides 
rise 19 feet; at the mouth of the Indus they are 
full 30 feet ; at St. Maloes, in France, 45 feet ; and 
at Cumberland, at the head of the Bay of Fundy, 
no less than 71 feet. This last is the highest in 
the world. 

Though the tides in open seas are at the high- 
est about two hours after the moon has passed the 
meridian, yet the waters in their passage through 
shoals and channels, and by striking against capes 
and head-lands, are so retarded, that, to different 



316 TIDES. 

places, the tides happen at all distances of the 
moon from the meridian. Other impediments to 
the course of the waters arise from the shallow- 
ness of the seas in some places, the intervention 
of continents, islands, and straits between them, 
&c. ; all which cause exceptions to the general 
rules here laid down ; but these can only be ex- 
plained from particular observations on the nature 
of the tides at particular places. 

Lakes have no tides, because they are generally 
so small that when the moon is vertical she at- 
tracts every part of them alike, and by rendering 
all their waters equally light, no portion of them 
can be raised higher than the rest. The Mediter- 
ranean and Baltic Seas have very trifling eleva- 
tions, because the inlets by which they communi- 
cate with the ocean are so narrow, that they 
cannot, in the short interval of the oceanic tides, 
receive or discharge enough sensibly to raise or 
sink their surfaces. 

Lines drawn through all the adjacent parts of 
a tract of water which have high water at the 
same time, are called co-tidal lines. 

The unit of altitude for a particular place, is 
the height of the maximum tide after the syzy- 
gies, being usually about 36 hours after the full 
moon. This is ascertained by measurement. For 
instance, its value for several places has been 
found as follows : 



TIDES. 317 

Cumberland, Bay of Fundy 71 feet. 

Boston 11 " 

New Haven 8 " 

New York 5 " 

Charleston, S. C 6 " 

The establishment of any port is the mean in- 
terval between noon and the time of high water 
on the day of new or full moon. When this is 
known, it may be used in computing the time of 
high water throughout the year. 

The great height of the tides in the Bay of 
Fundy is attributed to the meeting of the great 
northern and southern tide waves of the Atlantic, 
which here come together in opposite directions. 

Atmospheric tides undoubtedly occur, but they 
are too small and delicate in their nature to affect 
the barometer sensibly. 



APPENDIX, 



mjedler's elements of the orbits of the principal 
stellar systems, or binary stars. 



Stellar System. 



Period in 
years. 



Time of 
perihelion 



Mean year 
ly Motion. 



Ascending 
Node. " 



Inclina- 
tion. 



p Ophiuchi.. 
3062Struve. 
y Virginis . . 
\ Cancri.. . . 
\ Herculis . . 
q Coronae.. . 
a Coronae . . . 
co Leonis. . . . 
i Ursa Majoris 
a Geminorum. 
% Ophiuchi . . 



92.870 
94.765 

145.409 
58.910 
31.468 
43.246 

608.450 
82.533 
60.460 

232.124 



1812, 

1837, 
1836 
1853, 
1829 
1815, 
1826, 
1849, 
1816, 
1913. 
1798. 



— 232.58' 
+ 227.93 
—148.45 
—366.66 
—730.45 
+ 499.47 
+ 35.50 
+ 261.72 
—357.26 
— 93.05 
+ 245. 



126° 55' 
15 3 

60 38 

1 28 

39 26 

24 18 

25 7 
135 11 



95 

23 

184 



64° 51' 
35 31 
24 39 
63 17 
50 53 
71 8 
29 29 
46 33 
52 15 
70 58 
45°-50° 



Stellar System. 



p Ophiuchi. . . . 
3062 Struve . . . 

y Virginis 

I Cancri 

§ Herculis 

rj Coronae 

of Coronae 

o Leonis 

| Ursae Majoris 
a Geminorum . , 
a, Ophiuchi 



Perihelion 
from Node, 



142° 53' 
135 27 

78 22 
266 
262 4 
261 21 

64 28 
185 27 
129 41 

87 37 




Eccentri- 
city. 

0.4438 
0.4496 
0.8682 
0.2349 
0.4545 
0.3376 
0.6998 
0.6434 
0.4037 
0.7972 
0.37 



Semi axis 
Major. 



4.192" 

1.255 

3.402 

1.292 

1.189 

1.088 

3.918 

0.857 

2.290 

7.008 

1.1 



Cube root of 

mass x °y 

parallax. 

0.2044" 

0.0604 

0.1230 

0.0851 

0.1193 

0.0883 

0.0546 

0.0452 

0.1487 

0.1860 

0.05 

(319) 



320 



APPENDIX. 



struve's list of double and multiple stars, which, 
from their relative motions, are considered 
as physically connected together, or composing 
stellar systems, 

Class I. — distance of the components from 0" to 1". 



Certain. 


Probable. 


Suspected. 


36 Andromeda. 


7 Tauri. 


460 Struve Ceph. 


w Leonis. 


Atlas Pleiad. 


1500 Struve. 


y Virginis. 


s Equulei. 


287 Piazzi XVIII. 


42 Comae Beren. 


2384 Struve. 




1819 Struve. 






97 Coronae. 






y Coronae. 






% Ophiuchi. 






§ Herculis. 






2173 Struve. 






1 Ophiuchi. 






4 Aquarii. 






3062 Struve 







Class II. — distance from 1" to 2". 



Certain. 


Probable. 


Suspected. 


12 Lyncis. 

£ Cancri. 

1037 Struve. 

| Ursae Majoris. 
74 Piazzi XV. 
% Librae. 
a Coronae. 
2107 Struve Here. 
8 Cygni. 
127 Piazzi XIII. 


i Cassiopeiae. 
314 Struve Persei. 
32 Orionis. 
170 Piazzi VII. 
1768 Struve Can. 
93 Piazzi II. 


1338 Struve Lyncis 
1867 Struve Bootis 
73 Ophiuchi. 

429 Piazzi XX. 

185 Struve. 



APPENDIX. 



321 



Class III. — distance from 2" to 4". 



Certain. 


Probable. 


Suspected. 


s Hydrae. 


y Ceti. 


425 Struve. 


y Leonis. 


301 Piazzi VI. 


258 Piazzi IV. 


t Leonis. 


81 Virginis. 


742 Struve Tauri. 


s Bootis. 


g Herculis. 


£ Orionis. 


44 Bootis. 


49 Cygni. 


84 Virginis. 


8 Serpentis. 




39 Bootis. 


49 Serpentis. 




39 Draconis. 


(i Draconis. 




s Draconis. 


s Lyrae. 




4> c ygni- 


5 Lyrae. 




26 Piazzi XX. 


£ Aquarii. 




15 Monocerotis. 


2120 Struve Here. 




2309 Struve. 



Class IV. — distance from 4'' to 8". 



Certain. 


Probable. 


Suspected. 


Castor. 


38 Geminorum. 


41 Aurigae. 


£ Cancri. 


§ Coronae. 


1083 Struve. 


1263 Struve. 


1985 Struve. 


1121 Struve Offici. 


2 UrsaeMajoris. 


2725 Struve. 


v 1 Cancri. 


| Bootis. 


I* Cygni. 


1311 StruveCancri. 


% Librae. 


546 Struve. 


21 UrsaeMajoris. 


p Ophiuchi. 


1804 Struve Bootis. 


1813 Struve. 




2776 Struve. 


2917 Struve. 




3024 Struve. 


39 Eridani. 

583 Struve. 

625 Struve. 
1690 Struve. 
2263 Struve. 
2429 Struve. 



822 APPENDIX. 

Class, V. & VI. — distance from 8" to 16". 



Certain. 


Probable. 


Suspected. 


9j Cassiopeiae. 


14 Aurigae. 


570 Struve. 


1516 Struve. 


i Orionis. 


55 Eridani. 


61 Cygni. 


x Bootis. 


26 Aurigae. 


2760 Struve. 


a Equulei. 


19 Lyncis. 


23 Struve. 


248 Piazzi XXI. 


177 Piazzi XX. 


86 Struve. 


209 Piazzi XXII. 


|3 Cephei. 


2708 Struve. 


288 Struve. 


2848 Struve. 




i Leporis. 


221 Struve. 




1 Sagittae. 


9 Persei. 

563 Struve. 

719 Struve. 
1882 Struve Draco. 
2051 Struve. 






396 Piazzi XIX. 


Class VII. & 


VIII. DISTANCE FR 


om 16" to 32". 


Certain. 


Probable. 


Suspected. 


100 Piscium. 


83 Leonis. 


£ Piscium. 


1321 Struve. 


x Herculis. 


c Cancri. 


o Draconis. 


X Cygni. 


1283 Struve. 


8 Herculis. 


248 Piazzi XXI. 


1575 Struve. 


251 Piazzi 0. 


1132 Struve. 


Tt 1 Ursae Minoris. 


125 Struve. 


1616 Struve. 


2063 Struve. 


142 Struve. 




2703 Struve. 


447 Struve. 




51 Piscium. 


8 Equulei. 




26 Ceti. 
101 Struve. 
545 Struve. 
549 Struve. 

h UrsaeMajoris. 
44 Virginis. 
2115 Struve Here. 
250 Piazzi XIX. 

16 Lacertae. 
3039 Struve. 



APPENDIX. 



323 



struve's catalogue of stars, which, from their 
proper motions, are considered to be physi- 
CALLY DOUBLE, OR STELLAR SYSTEMS. 



Name of Stellar System. 



Distance of 
Components. 



61 

n 
p 

83 



Cygni 

Cassiopeiae 

Ophiuchi 

Leonis 

Herculis 

| Ursae Majoris . . . 

I Herculis 

5 Serpentis 

y Virginis 

42 Comae Berenicis. 

49 Serpentis 

X Cygni 

44 Bootis 

66 Ceti 

Persei 

9 Piazzi XI 

219 Piazzi XXII ... . 
88 Leonis 

i* Cygni 

84 Virginis 

33 Pegasi 

y Leonis 

a Coronae 

94 Aquarii 

4/ Draconis 

12 Canum 

yi Coronae 

17 Virginis 

y Ceti 

\ Piscium 

Castor , 

98 Piazzi III 

1 Ursae Majoris . . , 
a 2 Ursae Majoris . . 

y Coronae , 

Serpentis 

38 Piscium 

5 Lyrae 

s Lyrae 



16.0" 
9.5 
6.1 

29.6 

29.9 
1.8 
1.1 

10.1 
2.0 
0.0 
3.2 

25.8 
3.3 

15.5 

15.4 
1.1 
4.1 

15.3 
5.6 
3.4 
2.5 
2.5 
1.3 

13.4 

30.9 

19.9 
0.7 

19.3 
2.6 

23.5 
4.7 
6.1 

14.4 
4.6 
0.0 

21.6 
4.7 
2.6 
3.0 



324 



APPENDIX. 



GENERAL TABLES 



OF THE 



PRIMARY PLANETS. 





Mean Distance 
from the Sun, 
or Semi-Axis. 


Sidereal Revo- 
lution in Mean 
Solar Days. 


Eccentricity in 
parts of the Se- 
mi-Axis. 


Mercury 

Venus. 


0.3870938 
0.7233317 
1.0000000 
1.523691 
2.36148 
2.66946 
2.77091 
2.77263 
5.202767 
9.538850 
19.18239 


87.96928 
224.70078 
365.25637 
686.97964 
1325.485 
1593.067 
1684.735 
1686.305 
4332.58480 
10759.21981 
30686.82055 


0.2056163 

0.00686182 

0.01679226 

0.0932168 

0.088560 

0.255560 

0.0767378 

0.241998 

0.0481621 

0.0561505 

0.0466108 


Earth 


Mars 


Vesta 


Juno 


Ceres 


Pallas 


Jupiter 


Saturn 


Uranus 





Mercury. 
Venus . . 
Earth . . . 
Mars . . . 
Vesta.. . 
Juno... . 
Ceres . . . 
Pallas . . 
Jupiter.. 
Saturn , . 
Uranus. . 



Mean Longi- 
tude. 



112° 16' 4.8" 

146 44 55.8 

100 53 29.9 

233 5 33.9 

84 47 3.2 

74 39 43.6 

307 3 25.6 

290 38 11.8 

81 54 48.6 

123 6 29.3 

173 30 37.2 



Mean daily Mo- 
tion in Longi- 
tude. 


4° 5' 


32.6" 


1 36 


7.8 


59 


8.3 


31 


26.7 


16 


17.9 


13 


33.7 


12 


49.4 


12 


48.7 


4 


59.3 


2 


0.6 




42.4 



Longitude of 
the Perihe- 
lion. 



74° 20' 5.8" 
123 43 6. 

99 30 28.6 
332 22 51.2 
249 1137. 

54 17 12.7 
147 41 23.5 
121 5 0.5 

11 7 38. 

89 8 20. 
167 30 24. 



APPENDIX. 



325 



Mercury 
Venus . 
Earth . . 
Mars . . 
Vesta . . 
Juno.. . 
Ceres- . 
Pallas . 
Jupiter . 
Saturn , 
Uranus 



Inclination to 
the Ecliptic. 



5.9 
23 28.5 


51 6.2 
7 57.3 
2 10.0 
10 36 55.7 
34 35 49.1 

1 18 51.6 

2 29 35.9 
46 28.0 



7 
3 

1 
7 
13 



Longitude of 
the Ascending 

Node. 



Greatest Equa- 
tion of the 
Centre. 



45 57 9. 

74 51 41. 
0. 

47 59 38. 
103 20 28.0 
170 52 34.5 

80 53 49.7 
172 38 29.8 

98 25 45. 
Ill 56 7. 

72 59 21. 



23 40 43.0 
47 10.8 

1 55 27.6 

10 41 33.3 

10 9 26.7 

29 30 42.4 

8 47 58.2 

27 55 22.2 

5 31 13.6 

6 26 12.1 
5 20 32.8 





MeanDiameter. 


Volume. 


Mass. 


Mercury 


0.391 
0.985 
1.000 
0.519 
11.225 
9.022 
4.344 
112.060 
0.264 


0.060 
0.957 
1.000 
0.140 
1414.2 
734.8 
82.0 
1407124.0 

0.018 


2055 

24886 

27812 

3731 

9541984 

2855511 

401526 

1000000000 

321 


Venus 


Earth 


Mars 


Jupiter 


Saturn 


Uranus 


Sun 


Moon 







Density. 


Force of Gra- 
vity. 


Intensity of 
Light. 


Mercury • 


2.94 

0.923 

1.000 

0.948 

0.238 

0.138 

0.242 

0.252 

0.619 


1.15 
0.91 
1.00 
0.50 
2.45 
1.09 
1.05 
28.36 
0.163 


6.67 

1.91 

1.00 

0.43 

0.037 

0.011 

0.003 

1.00 


Venus • 


Earth 


Mars 


Jupiter 


Saturn 


Uranus 


Sun 


Moon 





Note. — In the above Tables the Elements of the Orbits of Vesta, 
Juno, Ceres and Pallas, are for 1831, July 23d. Oh., Mean Berlin Time. The 
others are for 1800, January 1st, Oh., Mean Paris Time. 

22 



QUESTIONS TO PART I. 

Sec. 1. 
general description op the heavens. 

What is the form of the surface of the heavens as it appears 
on a clear evening ? By what does this surface appear to be 
bounded ? What is the line called in which this plane intersects 
the heavens ? What bodies appear to move in this hollow sur- 
face ? And in what direction ? 

Describe the course pursued by a star which rises in the south- 
east. Where does it set ? What of the path of a star which 
rises farther from the south point of the horizon ? 

What is the Zenith ? What is the Meridian, and to what does 
it correspond ? How does it divide the paths or arcs described 
by the stars while above the horizon ? Are these arcs parallel or 
inclined to each other ? 

What portion of a circle is described by the stars in different 
parts of the heavens ? By one which rises near the north point 
of the horizon ? Are there any stars which never set ? What is 
their apparent course ? What are they called ? What is the 
star called about which they appear to revolve ? What is the 
North Pole of the heavens ? 

How do these motions, &c, correspond when observed on dif- 
ferent evenings ? 

Describe the general appearance of the heavens as viewed 
from the earth. What is this motion called ? What bodies 
appear to be fixed, and what bodies to move in the surface of the 
celestial sphere ? How might the apparent diurnal motion of 
the heavens be accounted for ? 

Sec. 2. 

PRELIMINARY DEFINITIONS. 

What is the Axis of the Heavens ? What are the North and 
South Poles? 

What is the Celestial Equator? How does it intersect the 
horizon ? 

(327) 



328 QUESTIONS. 

What are the Geometric Poles of the Equator ? What is a 
Great Circle ? What are the Poles of any circle ? The Poles 
of a great circle ? 

How is every circle divided ? How are Degrees, Minutes and 
Seconds marked ? Illustrate the use of these symbols by an 
example. 

What is a Declination Circle ? What are these circles some- 
times called ? 

What are Parallels of Declination ? 

What is a Vertical Line ? 

What are the Zenith and Nadir of any place ? 

What is the Meridian of a place ? Where does it cut the 
horizon ? 

What is a Vertical Circle ? The Prime Vertical ? 

What is the Ecliptic ? The Obliquity of the Ecliptic ? The 
Equinoxes ? When does the Sun pass them ? How are they 
named ? Where are the Poles of the Ecliptic ? 

What is the Equinoctial Colure ? 

Define Right Ascension. How does it compare with the lon- 
gitude of a place on the earth's surface ? How is it sometimes 
estimated ? How many degrees make an hour ? 

What is the Declination of a heavenly body ? When is it 
North and when South ? What Declination have bodies on the 
Equator ? To what is Declination analogous ? 

How are Right Ascension and Declination designated ? 

Sec. 3. 

CONSTELLATIONS. 

How were the heavens divided by the early astronomers? 
What kind of names were given to the Constellations ? What is 
said of their antiquity ? 

How are the Constellations bounded on the maps ? What are 
works of this kind sometimes called ? What is the correct 
title ? 

How are the stars in each Constellation distinguished ? Give 
an illustration. Mention some of the particular names of stars. 

Repeat the Greek Alphabet. Write the letters. 

By whom were these letters assigned to the stars ? Do they 
perfectly conform with the classification of the stars in the order 
of their brightness ? What does this show ? 



questions. 329 

Sec. 4. 

MAGNITUDES OF THE STARS. 

What can you say of the Magnitudes of stars ? The First 
Magnitude ? The Second ? The Sixth ? How is this classifica- 
tion extended to the telescopic stars ? 

How many Classes of telescopic stars does Sir John Herschel 
use ? Of what magnitude are the smallest according to his 
classification ? What is Struve's Classification ? Which Mag- 
nitudes are used in this book ? 

Sec. 5. 

A MORE PARTICULAR DESCRIPTION OP THE STARRY HEAVENS. 

Give an account of the appearance of the starry heavens on a 
clear evening. What causes the stars to twinkle ? Do they all 
twinkle ? What are those which do not called ? Why ? Why 
are the others called Fixed stars ? Into what classes are the 
fixed stars divided ? How numerous do they appear to be ? Are 
they so in reality ? What is the actual number visible at any 
time ? How many are there in the whole heavens in the first six 
classes? . How is the illusion of the apparent countlessness of the 
stars explained ? Have the stars all been counted ? What else 
has been determined about them ? What is required for obtain- 
ing a knowledge of the Stars ? What for a knowledge of the 
Earth ? 

What of the number of stars revealed to us by the telescope ? 
How do the six telescopic Classes compare with the first six ? 

How many stars of the sixth would it take to make one as 
bright as a star of the first magnitude ? How many of the 
twelfth magnitude must be grouped together to produce the same 
degree of brilliancy ? 

If all the stars were of the same size, what should be the dis- 
tance of those of the sixth, and what the distance of those of the 
twelfth magnitude, compared with those of the first ? If they 
were, besides, situated at uniform distances in space, what con- 
clusion might be formed respecting their numbers ? How many 
are there of the first class ? Of the second ? Of the third ? 
Of the fourth ? 

What is the probable number of the fifth magnitude ? Of the 
sixth ? 

How many might we expect to find in the several telescopic 
? 



330 QUESTIONS. 

How is this confirmed by observation? How many more 
might we expect a telescope, more powerful than any heretofore 
used, to reveal to us ? 

What can you say of the groups in which the stars present 
themselves ? 

Sec. 6. 

OF THE DOUBLE AND MULTIPLE 'STARS. 

What of the tendency to the formation of groups, as displayed 
on a close examination with the aid of a telescope ? 

What was Mitchel's opinion with regard to these double stars ? 
What was the result of the observations of the elder Herschel ? 
What brilliant discovery did he make ? How has this since 
been confirmed ? What discovery was afterwards made by Sir 
William Herschel ? What of Struve's works on double stars ? 
What was done by Sir J. F. W. Herschel ? What of Encke's 
method ? 

How many pairs and multiples of stars are there within 32" 
of each other ? To what must this great prevalence of double 
and multiple stars be owing ? By what name are these distin- 
guished ? What are the systems composed of two, three, &c M 
stars called ? What other class of double stars is there ? How 
are these named ? 

Do the Binary stars revolve around each other ? When are 
two stars said to revolve around each other ? 

By what force are the physically double stars acted upon ? 
What comparison is made between these and our solar system ? 

If we suppose an average to prevail in the size and brilliancy 
of the stars and in their distances apart, how many should we 
expect to find optically double in the first eight magnitudes ? 
What is the actual number of double stars in these classes ? 
How many of these should, by average, be optically double ? 
What of the remainder ? What are the indications of this con- 
nexion ? 

Of the triple and multiple stars, how many are supposed to 
form physical systems? At what does Msedler estimate the 
number of binary and ternary stars ? 

Sec. 7. 

COMETS. 

What is here said of Comets ? 



questions. 331 

Sec. 8. 

VARIABLE STARS. 

What are Variable Stars ? 

Describe the star o Ceti. What is its period ? What was its 
time of greatest brilliancy in 1844 ? How does its increase of 
light compare with its decrease ? 

Describe Algol. What of its vicissitudes of light ? What is 
its colour ? What is that of the other variable stars? 

What is its period ? Who discovered this star to be variable ? 

What can you say of the variable star in the Lion ? 

What of that in the Virgin ? 

Who discovered the variableness of the star in the Crown ? 
What is the peculiarity of this star ? 

What can you say of Ras Algethi ? 

Mention some other variable stars. 

What is the prevailing colour of variable stars ? Which phase 
of light lasts longest ? What star forms an exception to these 
rules ? 

What causes have been assigned for this remarkable variation 
of light ? 

What circumstance induced Hipparchus to make the first cata- 
logue of stars? Give an account of the star which appeared in 
a. d. 389. What of the new star seen in the ninth century ? 
Give a description of the one discovered by Tycho Brahe. What 
other new stars can you mention ? 

Is it probable that any stars have disappeared? How did 
Newton account for this ? 

Sec. 9. 

NEBULJE AND CLUSTERS OF STARS. 

Mention some of the most remarkable clusters of stars. In 
what does the Milky-Way abound ? What are these portions ? 

What can you say of the number of stars in some of these 
spots? What was Herschel's idea in reference to the position 
of our sun ? 

Give an account of the probable character of the Milky- Way. 
To what class of nebulre may it belong ? What must then be 
the position of our system to enable us to see it as we do ? 
Why? 

What does the nebulous region of the heavens embrace? 
Where is the most nebulous part of this zone ? 



662 QUESTIONS. 

What are Resolvable Nebula ? What of the number of stars 
contained by some of them ? 

How great is the distance of these clusters ? j What of the 
irregular clusters ? How were these regarded "By Sir William 
Herschel ? 

Are all the objects of this class resolvable into stars ? Why ? 

What are Irresolvable Nebula ? Describe them more particu- 
larly. What are the most remarkable examples of this class ? 
Describe them. Describe the annular nebula in Lyra. 

Describe the Planetary Nebula. What of their dimensions ? 

What is the fourth class ? Describe them. What are Nebu- 
lous Stars ? Mention some examples. 

Describe the Zodiacal Light. In what list of stars does this 
seem to place our sun ? What of the variety of forms of the 
stellar nebulae and nebulous stars ? 

What of the distribution of the nebulae over the heavens ? 
What analogy is there between the double and multiple nebulae 
and the binary and multiple stars ? 

What is the number of nebulae at present known ? What are 
Mrs. Somerville's views in regard to this nebulous matter ? 

Sec. 10. 

DESCRIPTION OF THE MAPS. 

Give a general description of the first two Maps. 

What do the next five represent ? 

Describe the eighth and ninth. 

What of the next five ? 

What is the use of the fifteenth ? 

Sec. 11. 

DESCRIPTION OF THE CONSTELLATIONS. 
Plate III. 

Name the Constellations in Plate III. 

Describe Ursa Minor. What of the magnitudes of the stars 
in it ? Tell the names of the principal stars. Describe the Pole 
Star. Give the history of this constellation. 

Where is Cepheus situated ? How may it be known ? What 
are the names of its principal stars ? Give its history. 

What is the situation of the Dragon ? Where is the Pole of 
the Ecliptic? What of the magnitudes of the stars of this con- 



aUESTIONS. 333 

stellation ? Of what does the head consist ? How many coils 
are there between the head and tail, and what of them ? What 
stars are near the tail ? For what is the star a remarkable ? 
Mention the proper names of the principal stars. What is the 
fabulous history of this constellation ? 

By whom was the constellation of the Lizard formed ? 

What of Honores Frederici ? 

Who established the constellation of the Grey-Hounds ? What 
names have been given to the two Hounds ? What of the star a ? 

What can you say of the constellation of the Mural Quadrant? 

How may the Swan be known ? Where does it lie ? In what 
is it very rich ? Give the names of the principal stars. Where 
is the double star " 61 Cygni" situated ? Describe it. For what 
will it be forever memorable ? What is their distance from the 
earth ? In what time does their light reach us ? Is this sup- 
posed to be the nearest star ? To what do the brightest probably 
owe, in a great measure, their great brilliancy ? What great 
discoveries have resulted from researches after the parallax of the 
fixed stars ? What is the history of this constellation ? 

Plate IV. 

Name the Constellations in Plate IV. 

What are the names of the principal stars in the Great Bear ? 
What is the Great Dipper, or Charles' Wain ? Which are the 
Pointers ? How can the right hinder leg be found ? The left 
hinder foot ? The right fore-foot ? 

Who instituted the constellation Custos Messium? Where 
does it lie ? 

When and by whom was Camelopardalis instituted ? What 
does it contain ? 

Where is Cassiopeia ? What are the principal stars ? Which 
is the brightest of these ? How can the position of the North 
Pole be determined by it? What remarkable discovery did 
Tycho Brahe make in this constellation ? What is said of the 
star ft ? Relate the fabulous history of this constellation ? 

What of the Little Lion, its situation, &c. 

By whom was the Lynx instituted ? 

Where is Perseus situated ? What are the principal stars ? 
How m&y Algenib be recognized? How Algol? For what is 
Algol remarkable ? Describe it ? Give the history of Perseus 
and Medusa's Head. 

By whom, and in memory of what, was the Reindeer estab- 
lished ? Where is it situated ? 

Where is Herschel's Telescope situated ? 



334 QUESTIONS. 

Plate V. 

Name the Constellations in Plate V. 

How may Pegasus be known ? What are the principal stars ? 
How may e in the nose be found ? How ? ? Relate the fable 
of Pegasus. 

Where does the constellation Andromeda lie ? What are the 
three principal stars ? How are they situated ? Mention some 
of the other stars with their situations. What four stars form 
nearly a square ? Relate the fable. 

Where is the constellation of the Triangles ? What is the 
principal star ? 

How is the Fly situated ? Of what is it composed ? 

How are the Fishes connected ? Where are they situated ? 
Relate the fable. When does the sun enter this sign ? 

How is Aries, or the Ram, recognized ? What are the princi« 
pal stars ? What is its fabulous history ? When does the sun 
enter this sign? What does this entrance constitute? What 
occurs at the poles at this time ? What of the days and nights 
at this period ? What is the position of the sun at this time ? 

Plate VI. 

Name the Constellations in Plate VI. 

What are the two principal stars in Auriga? How may this 
constellation be easily recognized ? What other small triangle 
is there ? What is the history of the Charioteer ? 

Name the most remarkable stars in the Bull. Where is a and 
what is it sometimes called ? How may it be known ? Where 
are 0, y and e ? Describe the cluster called the Hyades ? What 
other remarkable group of stars is there in this constellation ? 
How large a space does it occupy ? How many stars does it 
contain ? What are the names of the principal stars ? How 
many of them are visible to the naked eye ? Relate the fable of 
Taurus. That of the Pleiades. That of the Hyades. When 
does the sun enter Taurus ? 

What are the principal stars in the Crab ? Where is Proesepe 
or the Manger ? Describe it. Give the fabulous history of this 
constellation ? When does the sun enter Cancer ? 

Which is the most beautiful constellation in the heavens? 
What of the antiquity of Orion ? Name the principal stars. 
How are a, (3 and y situated ? How 6, z and £ ? What do they 
form ? What do *, a, y and /? form ? How is the sword formed ? 
What stars are in the shield ? Where is the star <r, and what is 
said of it? Where is the great nebula? Describe it. Wha* 
change does it appear to be undergoing ? In what does this con- 



QUESTIONS. 335 

stellation abound ? What is the peculiarity of these nebulous 
stars ? How does Herschel account for their variations ? What 
is the history of Orion ? 

How is the constellation of the Twins distinguished ? Where 
are y, £ and 6 ? Where is the star /* situated ? Relate the fable 
of Castor and Pollux. When does the sun enter this sign ? 

By whom was the Unicorn introduced ? Where does it lie ? 

How is the Little Dog distinguished ? What kind of a trian- 
gle does Procyon form with and y of the Twins ? What is 
the history of this constellation ? 

Plate VII. 

What Constellations are represented in Plate VII. ? 

Where is Bootes situated ? What are its principal stars ? 
How may Arcturus be found ? Where are the stars v and £ ? 
Where are y, /? and 6 ? What figure do they form ? Where is e ? 
Relate the history of this constellation ? 

What can you say of Lyra ? What of Vega ? What are the 
other principal stars ? Where is this constellation situated ? 
What stars in it form an equilateral triangle? Relate the fable 
of the Lyre. 

What are the principal stars in the constellation Hercules ? 
Where are they situated ? In what line are a, 8 and n ? What 
are the situations of £, <5, -k and e ? Where is /? ? What are the 
magnitudes of these stars? What interesting relation is there 
between our system and this constellation ? Who first conceived 
the idea of this motion ? Towards what point is our system 
ascertained to be moving ? With what velocity ? Give the his- 
tory of Hercules and the Cerberus. 

Where is the Northern Crown situated ? What are its two 
principal stars ? How may it be recognized? What is its his- 
tory ? 

Where is the Polish Bull? What of it? 

Plate VIII. 

Name the Constellations in Plate VIII. 

What are the names of the principal stars in the Great Lion ? 
How may Regulus and y be found ? What stars form a curve 
on the neck ? What constitute the Sickle ? Where is Denebola ? 
Tell how the other stars may be found. What is this sign sup- 
posed by the fabulists to be ? When does the sun enter it? 

What are the principal stars in the Virgin ? What can you 
say of Spica ? What do Spica, Arcturus and Denebola form ? 
Tell how the other stars are pointed out. How is the head 



336 QUESTIONS. 

marked ? Give an account of the stellar system of Virginis. 
Explain the drawing- of its orbit. What else can you say of this 
pair of stars ? Relate the fable of the Virgin. When does the 
sun enter this sign ? 

Describe Coma Berenices. What is its appearance to the 
naked eye ? Describe the pair of stars represented in the cut. 
What is the fabulous history of Berenice's Lock ? 

Where is the Sextant situated ? By whom was it instituted ? 

Plate IX. 

Name the Constellations of Plate IX. 

Who instituted the constellation Antinous ? What stars does 
it contain ? How may they be found ? 

Where is the Eagle situated ? What are its principal stars 1 
How may it be found ? 

Where do the Scales lie ? Name the principal stars. How 
may a be found ? Where is (3 ? With what stars does it form a 
nearly equilateral triangle ? What is the history of tins sign ? 
When does the sun enter it ? What then occurs ? 

What are the principal stars in the Serpent-Bearer ? Explain 
the method of finding the stars of this constellation. What four 
form nearly a rectangle ? Explain the cut of r Ophiuchi. What 
of the stellar system p Ophiuchi ? What is its period ? How 
does its orbit compare with that of y Virginis ? Give a full de- 
scription of this system, its peculiarities, importance, &c. Relate 
the fable. 

Where is the head of the Serpent, and what stars does it con- 
tain ? Where are a, <5 and e ? How is the direction of the tail 
indicated ? What are the names of the principal stars in the 
Serpent ? 

Where is the Dolphin situated ? What figure is formed by 
the four principal stars ? What star lies south-west of the 
rhombus ? Relate the fable. 

Where is Equiileus situated ? How may it be known ? What 
is this asterism said to represent ? 

By whom was Sobieski's Shield instituted ? Where is it ? 
How may it be found ? 

Where is the Solitary Thrush, and by whom was it established ? 

Where is the constellation of the Fox and Goose situated ? 
What else can you say of it ? 

Where is Sagitta, or the Arrow ? Relate the fable of the 
Arrow. 



QUESTIONS. 337 

Plate X. 

Name the Constellations in Plate X. 

What are the principal stars in Sagittarius ? Where does it 
lie ? Where is the Bow, and how is it marked ? How is the 
Arrow marked ? How does it point ? Give the history of this 
constellation. When does the sun enter this sign ? 

Name the principal stars in the Scorpion. Where is Antares ? 
What stars are west of it ? What of the stars in the extremity 
of the tail ? What is the fabulous history of this sign ? When 
does the sun enter it ? 

Where is Lupus, and what can be said of it ? 

Where is the Altar situated ? 

What is the situation of the Rule and Square ? By whom 
was it instituted ? 

Where is the constellation of the Telescope ? 

Where is that of the Southern Crown ? 

Plate XI. 

Mention the Constellations in Plate XI. 

What are the principal stars in Aquarius? Describe the 
figures formed by these with e and v. What stars are in the 
Urn ? Relate the fable. When does the sun enter this sign ? 

Name the principal stars in Capricornus. Where does this 
constellation lie ? What are the situations of the stars in it ? 
Give the history of this sign. When does the sun enter it ? 

Where is the Southern Fish ? By what star is it distinguished ? 
What does Fomalhaut form with (3 and £ ? 

Where is the Balloon situated, and by whom was it introduced? 

Where is the Microscope situated ? 

What can you say of the constellation of the Crane ? 

Where is the Phoenix ? 

Where does the constellation of the Sculptor's Tools lie ? 

Where is that of the Indian ? 

What can you say of the six last named constellations ? 

Plate XII. 

Name the Constellations in Plate XII. 

What are the principal stars in Cetus ? How may the head 
and neck be known ? How may the other stars be found ? 
What four form a parallelogram ? What is the history of this 
sea-monster ? 



338 QUESTIONS. 

Where is Eridanus ? What are the most important stars ? 
"Where may this constellation be traced ? How may the princi- 
pal stars visible in our latitude be found ? Relate the fable. 

What is the situation of the Hare ? By what four stars may 
it be known ? What are the other stars, and where ? 

Where is Harpa Georgii ? 

How is the Sceptre of Brandenburg situated ? Of what does 
it consist ? By whom was it formed ? 

Where is the Chemical Apparatus ? 

Where is the Electrical Machine ? 

Where is the Graver ? 

Where is the Clock ? Of what are the last six constellations 
composed ? 

Plate XIII. 

What Constellations are represented in Plate XIII. 

Name the most important stars in the Great Dog. Where is 
it situated ? What of Sirius ? Where are y and 0? What of 
S, e and n ? What do £, /?, a and t form ? Relate the fable. 

What are the principal stars of the Ship Argo ? What of Ca- 
nopus ? How may the prow of the ship be known ? Explain 
the method of finding the other principal stars. Give the his- 
tory of this constellation. 

Where is the Dove situated ? 

Where is the Cat ? 

Where is the Painter's Easel ? 

Where is the Printing Press ? 

Where is the Compass ? 

Plate XIV. 

Name the Constellations in Plate XIV. 

What is the extent of the constellation Hydra ? How may 
the head be known ? What is a called, and where is it ? How 
is the first coil marked ? Describe the course of the Water-Ser- 
pent. Relate the fable. 

Where is the Cup ? How may it be found ? What of its 
principal stars ? Give its history. 

Where does the Centaur lie ? What of it ? Give the history. 

Where is the Crow situated, and how may it be recognized ? 
What is its history ? 

Where is the Air-Pump situated, and by whom was it intra 
duced ? 



OUESTIONS. 339 

Where is Charles' Oak, and by whom was it placed in the 
heavens ? 

What can you say of the Cross ? What of these two and the 
constellations farther south ? Give the names of the latter. 

Describe the two Black Clouds. 

Describe the two Southern Clouds. 

Sec. 12. 

CA.LENDAR OF THE STARS. 

Note. — In studying this calendar the student should have fre- 
quent reference to the maps, and to the heavens. The calendar 
for the middle of the month may be adapted to any other day of 
the same month by allowing four minutes for each day before or 
after the fifteenth. Thus, the calendar for January is a repre- 
sentation of the heavens as they appear at half past nine o'clock 
on the 15th day, and as each star rises four minutes earlier each 
day than the preceding, they will evidently be in the same situa- 
tions on the first of the month one hour later, or at half past ten 
o'clock ; and on the 30th of the month at half past eight o'clock 
in the evening, or an hour earlier. 



QUESTIONS TO PART II. 



Sec. 1. 

What are the planets ? Why are they so called ? What of 
their motions ? 

How many planets are there ? Which of them were known 
to the ancients ? What of the other five ? When discovered, 
and what are their names ? What are primary planets ? What 
other bodies are there connected with these ? Of what is the 
jsolar system composed? 

Sec. 2. 

THE PTOLEMAIC SYSTEM. 

What was the supposition of the ancients in regard to the 
planetary system ? What difficulties did they encounter ? 

What was the system called, and by whom was it received ? 
What did Pythagoras maintain? How long did this system 
hold sway ? 



340 questions. 

Sec. 3. 
the copernican system. 

When was the Copernican System first promulgated ? Who 
was its author ? What is the arrangement of the bodies in this 
system ? 

What is the earth now proved to be ? 

What was supposed to be the form of the earth in the earliest 
ages ? What first induced people to consider it a sphere ? 

What other evidences have we of its spherical form ? Is the 
earth a perfect sphere ? 

What is the aspect of the heavens with reference to the hori- 
zon of a spectator upon the earth's surface ? Supposing the 
earth to be stationary, with what velocity must some of the fixed 
stars move ? What then must be the true cause of the apparent 
diurnal motion of the heavens ? 

Describe the apparent motions of the planets. Are these ap- 
pearances real ? How can they be explained ? 

Sec. 4. 

DEFI NI TI ONS. 

What are Planets ? Into what two classes are they distin. 
guished ? 

What is the centre of motion of the primary planets ? How 
many of this class are there ? Give their names and characters. 

What are secondary planets ? How many are there ? About 
which of the primaries do they revolve ? 

What is the orbit of a planet ? Where is the earth's orbit ? 

What are Nodes ? What are the two Nodes called and how 
are they marked ? 

What is meant by the term Aspect ? What is Conjunction ? 
What is Opposition ? 

What are the Syzygies? The Quadratures? 

When is a planet's motion said to be direct? When retrograde? 

What is a Digit ? Define a Disc. 

What are Geocentric latitudes and longitudes ? 

What are Heliocentric latitudes and longitudes ? 

What is the Apogee ? What the Perigee ? 

What is the Aphelion ? What the Perihelion ? What are 
these points sometimes called ? What is the Line of Apsides ? 

What is the Eccentricity of an orbit ? 



QUESTIONS, 341 

What is an Occupation ? What a Transit ? 
What is an Eclipse of the Sun ? What is an Eclipse of the 
Moon? 

What is the Elongation of a Planet ? 

What is a Diurnal Arc ? A Nocturnal Arc ? 

What are the elements of the Orbit of a Planet ? 

Sec. 5. 
kepler's laws. 

What curves do the planets describe about the sun ? At what 
point is the sun situated ? What can you say of the paths of 
comets ? 

Define the Ellipse. What is the Transverse Axis ? What 
are the Foci ? What is a Radius Vector ? 

By whom and how was this law discovered ? What is meant by 
a Conic Section ? When is it a circle, and when an ellipse? 
What is the Eccentricity of an Ellipse ? What is a Parabola ? 
What is an Hyperbola ? 

What is Kepler's Second Law ? Explain it ? When has a 
planet its greatest velocity ? How does the velocity vary ? 

How may this property be illustrated by experiment ? 

What is Kepler's Third Law ? Give the example. 

Does this law extend to the secondary systems ? 

Sec. 6. 

THE NEWTONIAN THEORY OP GRAVITATION. 

What can you say of Sir Isaac Newton's discovery ? 

What force causes the moon to revolve around the earth ? 
What is said of the extent of the influence of this force ? In 
what proportion does the force of gravity between two particles 
diminish ? How does it increase ? 

What can we infer from this law of gravity ? Explain. 

What is said of the extent of this law ? What knowledge 
may be derived from this fact ? What did Bessel determine con- 
cerning the stellar system 61 Cygni ? 

Sec. 7. 



THE SUN. 



What can you say of the sun ? To what class of heavenly 
bodies does it belong ? Why does he appear so much brighter 



342 QUESTIONS. 

and larger than the fixed stars ? What is his distance from the 
earth ? How long would it take a cannon ball to reach the sun ? 
How does he compare with the other fixed stars in that respect ? 

What is the figure of the sun ? His diameter ? His bulk ? 
In what time does he revolve about his axis ? How is this axis 
inclined ? Towards what points is it directed ? 

What is the sun supposed by some philosophers to be ? What 
is Sir William HerschePs hypothesis ? What causes the dark 
spots ? What the brighter spots ? What are these spots called ? 
What has been ascertained from observations of these spots ? 

What other singular phenomenon accompanies the sun ? De- 
scribe it. What is it supposed to be ? What does Professor 
Olmsted suggest ? 

What is the force of gravity at the sun ? How far does a 
body fall during the first second of time ? What would the phy- 
sical power of our men avail them there ? What of the sun as 
an habitation ? 

What is the proper motion of the sun, and towards what point 
is it directed ? What is the Uranographical effect of this mo- 
tion ? 

Relate the fable. What is the astronomical sign of the sun ? 

Sec. 8. 

MERCURY. 

Which planet is nearest the sun ? In what time does it revolve 
around the sun ? In what time about its axis ? What does this 
constitute ? Why is this period uncertain ? 

What is Mercury's distance from the sun ? At what rate does 
it move in its orbit ? What is his diameter ? What his appear- 
ance ? 

What are Mercury and Venus called ? Why ? What are the 
other planets called ? Which of the planets can never be in op- 
position ? What is their inferior conjunction ? What their 
superior ? 

How far can Mercury depart from the sun ? What of his 
phases ? 

What is a Transit of Mercury ? At what seasons can they 
occur ? Mention those which will occur during the remainder 
of the present century. 

What do the phases of this planet prove ? 

What is its density ? Its mass ? 

What can you say of the seasons of Mercury ? What of the 
intensity of its light ? What is the apparent diameter of the 



QUESTIONS. 343 

sun as seen from Mercury ? What is the variation in the length 
of its day ? 

How large does Venus appear from Mercury ? How does the 
earth appear ? How the other planets ? 

How does the weight of a body at Mercury compare with its 
weight at the earth ? How long is the seconds pendulum there ? 
What can you say of the compression of this planet ? 

What was Mercury considered to be by the mythologists ? 
What is the astronomical sign of this planet ? 

Sec. 9. 

VENUS. 

What is the distance of Venus from the sun ? In what time 
and at what rate does she revolve around him ? What is the 
time of her diurnal rotation ? What is her magnitude ? 

What is the appearance of Venus, her phases, spots, &c. ? 

What of Venus' apparent diameter ? Explain the drawing. 

What can you say of the difference in her seasons ? 

How far does this planet ever recede from the sun ? When is 
she called the morning star and when the evening star ? How 
long does she continue to be one or the other ? 

What can you say of the telescopic appearance of Venus ? 

What of its Transits ? At what intervals do they happen, and 
in what months ? Give a list of all the Transits from 1639 to 
the 22d century. 

What can you say of the observations of that of 1769 ? What 
result did Encke deduce from them ? 

What is the intensity of the sun's light at Venus ? What is 
his apparent diameter ? 

Which is the most brilliant body in the evening sky of Venus? 
How does our moon compare with Mars there ? What of the 
phases of the earth ? What of the eclipses of our moon, and its 
Transits over the earth's disc ? 

What of the weight of bodies at Venus ? 

Sec. 10. 

THE E ARTH. 

How far is the earth from the sun ? What is its diameter ? 
Its circumference ? Its surface I What is its mass ? What is 
its density ? 

What is the figure of the earth ? What was the opinion of 



344 QUESTIONS. 

the ancients in regard to this ? How is the spherical form 
proved ? How has the flatness of the earth at the poles been 
ascertained ? 

What is the centrifugal force at the equator ? If the velocity 
of the earth was 17 times as great as it is, what would bodies 
weigh at the equator ? 

How does the compressed form of the earth affect the weight 
of bodies on different parts of the surface ? 

What can you say of the fall of a body in the first second ? 

What of the length of the seconds pendulum ? 

What are the sensible motions of the earth ? Describe the 
annual revolution. Describe the diurnal rotation and its effects. 

What are the insensible motions ? 

How is the alternation of day and night produced ? How 
may this be illustrated by experiment ? 

At what places are there but one day and one night ? How is 
it with places within the polar circles ? Explain this. 

W 7 hat can you say of the twilight in the polar regions ? What 
of the light of the moon ? 

Upon what does the variety of the seasons depend ? What 
constitutes a summer season, what a winter, and what a spring 
or autumn ? 

What are the seasons in December ? What in March and 
September ? 

How are the changes of the seasons illustrated by the diagram ? 

What can you say of the earth's satellite ? How does the 
earth appear as seen from the moon ? When we have new moon, 
what phase does the earth present to the moon ? 

What is the Atmosphere ? How does it affect the rays of 
light? What would be the appearance of the heavens by day 
without it ? What are produced in it ? 

What can you say of its density ? What of its height ? Its 
weight ? 

What is the mass of the atmosphere ? What would be its 
height if its density were the same throughout as at the earth's 
surface ? What is its greatest possible height ? Why ? How 
does it« temperature vary at different heights ? 

How does the atmosphere affect the apparent positions of the 
heavenly bodies ? 

What is the amount of refraction at the horizon ? What at 
45° of altitude ? What in the zenith ? 

What constitutes wind ? How are clouds and rain produced ? 



QUESTIONS. 345 

What can you say of the position of the axis and of the poles 
with regard to the earth itself? What of the position of the 
axis in space ? What circle is described by the north pole, and 
in what period ? Give the list of north polar stars. How long 
has our present pole-star held that rank, and how long will it 
continue to hold it ? 

W T hat can you say of the south polar stars ? 

With what consequence is this change in the position of the 
axis attended ? 

What will be the position of the celestial equator 12,000 years 
hence ? 

Give an account of the second variation. 

What is meant by a perturbation of the motion of a planet ? 

What is the third variation ? When is the earth nearest the 
sun? When will this happen 58 years hence ? When will it 
happen 10,000 years hence ? How will this affect the duration 
of the seasons ? How the temperature ? What is the eccentri- 
city of the earth's orbit ? 

What is the astronomical symbol of the earth ? 

Sec. 11. 

SATELLITES OR MOONS. 

What can you say of the proximity of the moon ? Of what 
do we know the existence, and of what the absence ? 

What have the satellites in common with their primaries ? 

What can you say of the times of rotation of the satellites 
about their axis ? What follows from this ? How is this of ad- 
vantage to them ? 

What other consequence of the equality of their periods of 
rotation and revolution can you mention ? Define Libration. 

What is the largest body in the firmament of a satellite ? Is 
it visible from all parts of the secondary ? 

What can you say of the phases of the primary ? Their pe- 
riod ? Give a more particular account of these phases as they 
appear from different parts of the surface of the moon. What 
Can be said of eclipses of the sun as they occur for each satellite ? 
What of the eclipses of the primaries ? 

Which are best adapted for observations of the heavens, the 
primaries or the secondaries ? 

How does the force of gravity at the surfaces of the moons 
compare with that at the surfaces of the primaries ? 

What is said of the importance of this element ? What is the 
ratio of the forces of gravity at the sun, the earth and her moon ? 



346 questions. 

Sec. 12. 

THE MOON. 

To what class of bodies does our moon belong" ? Whence 
does she receive her light and heat? Around what bodies does 
she revolve ? At what rate does she move around the earth, and 
at what distance ? In what time does she complete this revolu- 
tion ? What is this called ? What constitutes a sidereal revolu- 
tion, and in what time is it performed by the moon ? 

What is the moon's diameter ? How does her bulk compare 
with that of the earth ? What is the direction of the moon's 
apparent motion, and to what is it owing ? In what direction 
does the moon actually move ? How may this be ascertained ?• 

In what time does the moon revolve about her axis ? What is 
the consequence of this ? What causes a slight variation in the 
face which she presents to us ? What is the moon's libration in 
longitude ? Its amount ? What is her libration in latitude ? 
To what does it amount ? 

How many days and nights has the moon in one of our lunar 
months ? Of how many of her days does her year consist ? 
What of her seasons ? 

What can you say of the light which the earth reflects upon 
the moon ? 

Give an account of the variation of the phases of the moon. 

When does the disappearance take place? What is this 
called ? What phase does she present when she is in opposition ? 
How does she appear when in her quadratures ? In what is she 
then said to be ? 

On which side is the illuminated part from the change to the 
full? 

What is an eclipse of the sun, and what an eclipse of the 
moon ? When can the former occur ? When the latter ? Why 
do eclipses not occur at every new and full moon ? What is the 
greatest number that can occur in a year ? What the least ? 

What can you say of the harvest moon ? 

What of the full moon as seen through a telescope ? When 
are the mountains best observed ? 

How must the heavens appear at our moon ? Give an account 
of the advantages of clear sky, &c, possessed by the moon. 

How large does the sun appear when seen from the moon ? 
How large does the earth appear ? 

What is the length of the day at the pole of the moon ? How 
far below the horizon can the sun descend ? How and where 
would it be possible for a person to attain perpetual sunshine ? 



/ 

QUESTIONS. 347 

What is the length of the lunar year ? What of the difference 
of the seasons ? Why ? 

When the moon is totally eclipsed at the earth, what occurs at 
the moon? What phenomena occur at the moon when at the 
earth the following- happen, viz : a partial eclipse of the moon, a 
passage of the penumbra of the earth over the moon, a total 
eclipse of the sun, an annular or partial eclipse of the sun ? 

What can you say of the occultations of the fixed stars by the 
earth ? 

How does the earth constitute a time-piece for the moon? 

Give a general description of the character of the surface of 
the moon. How high are some of the mountains ? What can 
you say of the mountain ranges ? 

What of the circular ranges of mountains ? What do they 
resemble ? What are walled planes ? 

Which is the deepest cavern in the moon ? Describe it. 

Describe the crater-formed elevations. Are the volcanoes be- 
lieved to be in action or extinct ? What is supposed to be the 
cause of their present inactivity ? 

Describe the central mountains. 

Describe the spot called Tycho. Why are the spots called 
seas, lakes, gulfs, &c. ? What names have been given to many 
of these objects ? 

Mention the heights of some of the mountains. 

What is the astronomical sign of the moon ? 

Sec. 13. 

MARS. 

How may Mars be known in the heavens ? Whence does this 
proceed ? 

How far is Mars from the sun? At what rate does he move, 
and in what time does he make a revolution around the sun ? 
What is his diameter ? What his form ? How does his size at 
the opposition compare with that at the conjunction? Why? 
What of the light and heat at Mars ? 

How does Mars appear when viewed through a telescope? 
What is the inclination of the plane of his orbit ? What is that 
of his axis ? What are his greatest and least apparent diame- 
ters? What are his volume, his density, his mass? What 
would a body weighing a pound here, weigh at Mars ? 

What can you say of the spots on the surface of this planet, 
and of their cause ? 



348 QUESTIONS. 

From what is the existence of an atmosphere inferred ? De- 
scribe the spot at the south pole. 

What is the period of rotation of Mars ? 

How many martial days are there in his year ? What are the 
lengths of the seasons respectively ? 

What occasions this great inequality in the lengths of the sea- 
sons ? Into what zones may the surface of Mars be divided ? 
What can you say of the inequality of the days at Mars ? 

Which of the planets are Inferior with respect to Mars ? De- 
scribe the appearance of the heavens from Mars. 

How large does the sun appear there ? 

Towards what points are his poles directed ? 

What is the astronomical sign of Mars ? 

Sec. 14. 

VESTA . 

By whom and when was Vesta discovered ? What is its ap 
pearance ? Its diameter ? What is its distance from the sun t 
Its period of revolution ? What is the inclination of her orbit ? 
What else can you say of this planet ? What is its symbol ? 

Note. — The above questions may be applied to Juno, Ceres 
and Pallas, Sections 15, 16 and 17. 

Sec. 18. 
general remarks concerning the asteroids. 

What was Dr. Olbers' idea with respect to the origin of Ceres, 
and to what did it lead ? 

What remarkable conjecture had Professor Bode made previ- 
ously to the discovery of Ceres ? On what ground ? 

What knowledge have we respecting the magnitudes, rotations 
and positions of the axes of the Asteroids ? Which is the largest ? 
What is the surface of Vesta ? 

To what is our information concerning these bodies confined ? 
Which of the orbits are most eccentric ? 

What are their inclinations ? What name has been given to 
them in consequence of this ? 

What are their mean distances ? 

What are their periods of revolution ? What can you say of 
the distances and periods of Ceres and Pallas ? Do they move 
in the same path ? How do their orbits differ ? 



QUESTIONS. 349 

Describe the appearance of the heavens as seen from the 
Asteroids. 

Sec. 19. 

JUPITER. 

What is the magnitude of Jupiter ? In what time does it 
make a revolution, and what is his distance from the sun ? What 
is his rate of travelling- ? 

In what time does he revolve about his axis ? How does his 
rotary velocity compare with that of the earth ? Of what does 
his year consist? How does his equatorial compare with his 
polar diameter ? Of what is this a consequence ? 

What can you say of the density and mass of Jupiter ? 

What is the force of gravity at his surface ? 

Is the weight of bodies the same on all parts of Jupiter's sur- 
face ? What is the cause of this difference ? 

What can you say of the centrifugal force at the equator of 
Jupiter ? What is the length of the seconds pendulum at his 
equator ? At his poles ? 

What can you say of the difference of seasons at Jupiter ? 
Why is it so slight? 

What is the intensity of light and heat there ? How large 
does the sun appear there ? 

With what velocity do the stars appear to move there ? 

What can you say of the view of Saturn from Jupiter ? How 
large does it appear ? What of the transits of the inferior 
planets ? 

Describe the belts of Jupiter. How many are sometimes seen ? 
What are they supposed to be ? 

Give an account of the spots upon Jupiter's surface. 

What can you say of the bright spots sometimes seen? 

How many moons has Jupiter ? Who discovered them ? 
What are their periods of revolution ? What can you say of 
the eclipses of these moons ? Of what practical use are they to 
us ? What important law of light have they been the means of 
demonstrating ? 

What is the greatest ornament of Jupiter's sky ? What are 
their apparent diameters ? What else may be said of them ? 

What portion of the primary can be seen from one of these 
moons ? 

In what direction do the satellites revolve ? In what planes ? 
How do they appear to move when viewed from the earth? 



350 QUESTIONS. 

How often are the first three satellites eclipsed ? How often 
is the fourth ? At what intervals does the first suffer a total 
eclipse ? 

What can you say of the amount of Jupiter's moonlight ? 

What portions of his surface have no moonlight ? 

What of the retrograde motion of Jupiter ? 

What heavenly bodies may be observed at Jupiter ? 

Relate the fabulous history. 

Sec. 20. 



Which is the tenth planet from the sun ? What is his mean 
distance ? His diameter ? His velocity ? His period of revolu- 
tion ? His time of rotation ? The inclination of his orbit ? 
How is his axis inclined to the plane of his orbit ? 

What is the apparent diameter of Saturn ? Describe the rings. 

In what plane do they lie ? By what are they separated ? 
What is their thickness ? 

Describe Saturn as represented in the frontispiece. From what 
is it evident that the ring is a solid opaque substance ? What is 
the position of the axis ? 

What can you say of the parallelism of the axis ? In what 
time do the rings rotate ? In what plane ? 

How is their plane inclined to the ecliptic ? What are the 
nodes of the ring ? Where are they ? Under what form do the 
rings appear to us ? Give an account of the variations in the 
form of the rings, their disappearances. How often does the 
ring disappear from our view ? How does the ring vary after 
the planet has passed one of the nodes ? What is its form when 
the planet is 90° from the node ? What is the ratio of the two 
diameters then ? Explain the figure. 

Are the rings of uniform thickness and density throughout ? 
What is the position of the centre of the ring ? 

Describe the spectacle presented by the rings of Saturn to the 
inhabitants of that planet. How do they appear to those on the 
equator ? How to the inhabitants of the polar regions ? 

How are the rings illuminated during one half of Saturn's 
year ? What is the condition of the portion of the surface of 
the planet towards the sun ? What is that of the portion lying 
under the dark side of the rings ? 

Of how many days does Saturn's year consist ? What are 
the durations of its seasons ? What is the intensity of light 
there ? How large does the sun appear there ? 



QUESTIONS. 351 

What is the force of gravity at the poles of Saturn ? What is 
the length of the seconds pendulum there ? What is it at the 
equator ? 

What can you say of the apparent diurnal motion, &c, of the 
stars for Saturn ? 

How many satellites has Saturn? What can you say of their 
magnitudes ? 

What is the peculiarity of the phases of these moons, and what 
is the cause of it ? 

At what intervals does the first satellite pass the meridian of a 
given place on the surface of Saturn ? Explain it. 

At what seasons can the eclipses of these moons occur ? Dur- 
ing what length of time will the innermost satellite be eclipsed 
at every full moon ? How is it with the others ? How often do 
these satellites cause eclipses of the sun ? 

What can you say of the appearance of these moons from the 
earth ? What of the most distant ? In what time is it supposed 
to make a rotation about its axis ? What of the first three ? 
How were they seen by Sir William Herschel ? 

What can you say of the orbits of these satellites ? 

Sec. 21. 

URANUS. 

By whom and when was Uranus discovered ? What name did 
he give it ? By what other name was it called by foreigners ? 
What was the reason for calling it Uranus ? 

Describe this planet ? 

What is its mean distance from the sun ? His diameter ? 
His bulk ? What is the inclination of his orbit ? 

What is the period of his revolution around the sun, and what 
is his velocity ? What is his time of rotation ? 

How much light does this planet receive from the sun ? 

How large is the sun as seen from Uranus ? 

What can you say of the situation of Uranus in regard to ob- 
servations of the other bodies of the system ? What bodies are 
visible in his heavens at midnight ? 

Is this planet much nearer any of the fixed stars than we are ? 

What can you say of the annual parallax of the fixed stars at 
Uranus ? 

What is the greatest peculiarity of the Uranian system ? 

What can you say of the phases of these moons ? 



352 QUESTIONS. 

What of the eclipses of these moons and of the sun ? During 
what length of time will there be no eclipses ? 

What is the density of Uranus ? What of the weight of bodies 
at its surface ? 

What constitutes our whole knowledge of these bodies ? 

Sec. 22. 

COMETS. 

What other class of bodies belong to our system besides the 
primary and secondary planets ? 

What is the number of comets on record ? What of the first 
450 of these ? What of the rest ? How many comets are esti- 
mated to have visited our system since the creation ? What 
estimate may be formed of the number, including those too far 
off to be seen at the earth ? 

Of what three principal parts is a comet composed ? What 
can you say of the head ? Mention the diameters of the heads 
of some comets. 

What of the nebulous envelope ? 

What is the tail ? Is it ever wanting ? What is then the 
shape of the nebulous envelope ? What can you say of the 
curved tails which some comets have ? 

Have comets ever more than one tail ? What of the comet 
of 1823 ? That of 1744 ? That of 1811 ? 

What can you say of the comet of 371 years b. c. ? That of 
43 years b. c. ? What was it supposed to be ? What does Se- 
neca say of the comet of a. d. 60 ? What of the comets of 1402 ? 
How long was the tail of the ccmet of 1456 ? Describe the tails 
of the comets of 1618, 1680 and 1689. Describe the comet of 
1744. What was the length of the tail of the comet of 1843 ? 

Mention the real lengths of the tails of some comets? 

To what do the tails of comets owe their origin ? What is 
their general character ? 

Do comets shine by their own light? How is the nebulous 
envelope supposed to be formed ? What is probably their condi- 
tion when farthest from the sun ? 

What is the effect of the heat of the sun as the comet ap- 
proaches it ? What is said of the nature of these substances ? 
What is the force that governs the distance of the particles ? To 
what force is the formation of the tails attributed ? Explain it. 

In what case is the tail long and narrow? When the comet's 
head and the cometary repulsion are greater, what is the form 
of the tail? 



QUESTIONS. 353 

What becomes of the particles that form the tails of comets ? 

What was the opinion of the ancients concerning comets ? 

What was the effect of the appearance of Halley's comet, in 
1456, on the minds of the people ? 

Is it probable that comets have any effect upon the seasons ? 

What other source of apprehension is there ? Is there any 
probability of the head of a comet striking the earth ? 

If such a shock should occur, what might be the consequences? 
What is said of the mass or weight of many comets ? 

How does the comet of ] 770 confirm this ? 

Are the elements of the orbit of a comet the same as those of 
the planetary orbits ? Which of these cannot generally be de- 
termined for a comet ? 

What is the average of all the inclinations of the planes in 
which the comets move ? 

What is the shape of their orbits ? 

In what curves do all comets probably move ? Why ? Why 
do astronomers sometimes derive hyperbolic orbits ? 

What was the orbit of the comet of 1843, as computed by ob- 
servations made at the High School Observatory ? 

What is the estimated average period of revolution of comets? 
What number of comets have been observed and their elements 
computed ? 

What is the period of Halley's comet? What is the inclina- 
tion of its orbit ? What is its least, and what its greatest dis- 
tance ? What is its eccentricity ? Why is it named after Hal- 
ley ? How long does it remain within the orbit of the earth 
when at its perihelion ? How near may it approach to the earth ? 

Mention the dates of the supposed appearances of this comet, 
and the circumstances attending some of these appearances. 

When was its first certain appearance ? Describe it. When 
was its next ? When its third ? What can you say of its 
fourth, in 1682 ? 

What period did Halley assign to it ? When did he predict 
its return ? When did it return ? By what was it retarded ? 
What is said of its return in 1835, and of our knowledge of its 
period ? 

When was Olber's comet discovered ? What is its period ? 
Its inclination ? Its least distance ? Its greatest ? Its eccen- 
tricity ? When will it return to its perihelion ? 

What is Encke's comet sometimes called ? What is its pe- 
riod ? Its inclination ? Its eccentricity ? What are its least 
and greatest distances ? 



354 QUESTIONS. 

By whom and when was it discovered ? Who first ascertained 
its period ? By whom had it been seen ? What of its returns 
from 1825 to 1842 ? How did it appear in 1838 ? 

What did it furnish Encke the means of determining ? How? 

What resistance does this comet encounter while it is within 
the orbit of Venus ? 

How does this affect its period ? How its mean distance ? 

What theory does Encke resort to for a cause for these changes? 

What are the grounds for adopting this theory ? 

Give a more particular account of this theory ? 

When will the next returns of Encke' s comet take place ? 

Describe Gambart's comet. What are its period, inclination, 
&c? 

When was this comet last seen ? Why was it not visible in 
1839? 

When is it expected to be visible again ? 

What is said of the comets of 975, 1264 anc 1 1556 ? 

What of that of 1680? 

What of that of 1770 ? How did La Place account for this ? 

What is said of the great comet of 1843 and its probable 
period ? 

Describe the third comet of 1843. What is its period accord- 
ing to various authorities ? What is its inclination ? Its eccen- 
tricity ? 

What is said of the influence of Jupiter on this comet ? 

Between what does this seem to form a connecting link ? 

What is remarked of the position of its orbit in the heavens ? 

Sec. 23. 

ECLIPSES OF THE MOON. 

What kind of shadows must the earth and moon carry with 
them around the sun ? Why ? What constitutes a lunar eclipse ? 
At what times only can they happen ? Why do they not happen 
every full moon ? 

What constitutes a partial eclipse ? When is the eclipse said, 
to be total ? When central ? 

Where does the shadow of the earth terminate? What is its 
breadth at the point where the moon passes through it ? 

What are digits ? What is meant by the quantity of an 
eclipse ? 



QUESTIONS. 355 

On what does the duration of a lunar eclipse depend ? What 
is the longest duration of a partial eclipse ? Of a total eclipse ? 

Explain the figure. What is the umbra ? What is the pe- 
numbra ? 

When does the moon begin to lose sight of the sun ? When 
does the eclipse begin as seen from the earth ? When does it 
end? 

What renders it difficult to distinguish the line of separation 
between the umbra and penumbra ? Are these eclipses of much 
importance ? 



ECLIPSES OP THE SUN. 

What causes an eclipse of the sun ? When can these eclipses 
occur ? Why do they not happen every new moon ? 

Explain the figure. 

At what places is the sun centrally eclipsed ? At what places 
is the eclipse total ? At what places is it partial ? Upon what 
does the magnitude of the partial eclipse at any place depend ? 

What is an annular eclipse ? 

If, at the time of conjunction, the moon is so far from its node 
that the shadow does not touch the earth, what takes place ? 

What is the greatest breadth of the path of the shadow of the 
moon over the surface of the earth ? When does this occur ? 
Of what kind will that eclipse be which happens when the moon 
is in its apogee and the earth in its perihelion ? What is the 
greatest breadth of the path traversed by the penumbra when it 
falls perpendicularly on the surface of the earth ? Is an eclipse 
of the sun visible to all the inhabitants of the earth ? Do all see 
it alike ? What is the greatest breadth of that part of the sur- 
face at which the eclipse is annular ? 

What is the longest time that an eclipse can continue total? 
How long annular ? 

What are the limits for eclipses of the sun ? What are they 
for lunar eclipses ? 

How many eclipses can there be in a year ? How few ? Of 
which kind are these two ? When there are seven, how many 
are of the sun ? 

How do the eclipses occur in a series of 223 lunar months ? 
Explain this. How many eclipses are there in this period? 
How many of these are of the sun ? 

What was this period called by the Chaldeans ? 



356 questions. 

Sec. 24. 

TIDES. 

What is the tide ? What causes it ? What are the rising and 
falling tides denominated ? What is the average interval between 
two successive high or low tides ? 

What are spring tides ? What are neap tides ? When do 
they occur ? At what seasons of the year are the tides higher 
than usual ? 

Describe the motions of the waters of the sea, rivers, &c, dur- 
ing the rising and falling of the tides. 

What variation in the time of high water occurs each day ? 

When is the retardation in the time of high water least, and 
when greatest ? What other circumstances have an effect on the 
retardation of the tides ? What of the tides when the moon has 
a north declination ? What when her declination is south ? 

What shape would the waters in the ocean assume, were there 
no influence from either sun or moon, and the earth at rest ? 
What would be the case if the earth and moon were without 
motion ? 

How does the moon cause the particles of water immediately 
under her to rise ? How those diametrically opposite ? 

How much greater is the moon's attraction for the water im- 
mediately under her than for the centre ? 

If the earth were entirely covered by the sea, what form would 
the waters attracted by the moon assume ? Which is the greater, 
the elevation or the depression ? How do the effects of the sun's 
attraction compare with those of the moon's ? 

Does the summit of the waters point towards the moon ? 
Why ? How far from the meridian under the moon is it gene- 
rally high water in the open sea ? On which side of this meri- 
dian is the tide flowing ? How is it on the east side ? How is 
it 90° distant? How often must these tides happen? Why? 

What is the ratio of the forces with which the sun and moon 
move the waters ? How do the spring compare with the neap 
tides ? What constitutes the former ? What the latter ? 

Why do the tides rise higher at some seasons than at others ? 

What is the interval of time between the moon's passing the 
meridian and high water ? 

Do the tides always answer to the same distance of the moon 
from the meridian, at the same place ? How are they affected ? 

When will the greatest spring tide happen ? When the least I 
At what seasons of the year do the greatest tides occur ? 



QUESTIONS. 357 

Do the highest tides occur just at the time of new or full 
moon ? How long after ? 

How do the evening tides compare with the morning tides at 
places remote from the equator ? How is this explained ? When 
is this inequality greatest ? To what does it amount at the 
poles ? 

Where do the tides rise highest ? How is this accounted for ? 
What is the general elevation of spring tides in the open sea ? 
What is that of neap tides ? How high do the spring tides rise 
at London, the mouth of the Indus, St. Maloes, Cumberland ? 

Is it high water at all places when the moon is at the same 
distance from the meridian? What impediments are there to 
the course of the waters ? 

Why have lakes no tides ? What is said of those of the Medi- 
terranean and Baltic Seas ? 

What are Co-tidal Lines ? 

What is meant by the Unit of Altitude of a place ? What are 
those of Cumberland, Boston, New Haven, New York, Charles- 
ton ? 

What is meant by the establishment of a port ? 

To what is the great height of the tides in the Bay of Fundy 
attributed ? 

What is said of atmospheric tides ? 



QUESTIONS ON THE MAPS. 



Plates I. & II. 

Note. — These two plates contain the principal stars in each 
constellation, connected together by lines which form a variety 
of geometrical figures. The inner circle is divided into degrees 
of Right Ascension, and the outer into twelve parts, correspond- 
ing to the months of the year. The latter division is intended 
to show what stars pass the meridian at nine o'clock in the even- 
ing, at any season of the year. Thus, on the first of January 
all the stars in R. A. 56° will be on the meridian at nine o'clock ; 
those having a few degrees more R. A. will be found a little east, 
and those having a few degrees less, a little west of the meridian. 
And on the 10th of January, all the stars in R. A. 66° will be on 

24 



358 QUESTIONS. 

the meridian at nine o'clock in the evening. To a person in 
north latitude, the stars surrounding the north pole within a dis- 
tance from it not exceeding the latitude of the place, will be 
always visible ; and those within the same distance of the south 
pole will always be invisible to him. 

It must be remembered that Right Ascension is reckoned from 
west to east, in ascertaining the directions of the stars on the 
map from one another and from the meridian. 



What constellations are on the meridian and above the horizon 
of Philadelphia, (latitude 40° N.), at nine o'clock in the evening, 
on the 1st of January ? On the 26th of February ? On the 5th 
of May ? On the 15th of August ? On the 20th of November ? 

What constellations are always above the horizon of Philadel- 
phia ? What are always below it ? What stars lie within 10° 
of the equator on the north ? What on the south ? What stars 
lie on the ecliptic ? Through what constellations of the northern 
hemisphere does the ecliptic pass ? Through what southern con- 
stellations does it pass ? 

Plate III. 

Name the constellations on this plate. How are the Grey- 
Hounds bounded ? What part of the Great Bear lies north of 
them ? What is the extent of this constellation in Right Ascen- 
sion ? What in Declination ? What are the R. A. and Dec. of 
a or Cor Caroli ? 

By what constellations is the Little Bear bounded ? What is 
the brightest star in this constellation ? What figure do the 
principal stars form ? Draw it, and give the names of the stars 
composing it. 

How is the Dragon bounded ? What are the R. A. and Dec. 
of the head ? Mention the principal stars in the head. What 
part of the Dragon lies between the Pole Star and the Lyre ? 
Where are the other coils ? Where is the tail ? 

Where is the Quadrant ? How is it bounded ? 

How is the Swan bounded ? Give the situations of a, /?, y, £, 
and £, and their Right Ascensions and Declinations. What figure 
do these five stars form ? Which two point towards the Pole 
Star ? What is the extent of this constellation in R. A. ? What 
in Dec. ? 

What small constellations lie east of the Swan ? How are 
they bounded on the north ? How on the south ? What is east 
of the Glory of Frederic ? What west ? 

How is Cepheus bounded ? What figure is formed by ft a and 



QUESTIONS. 359 

tj ? What by a, rj and % • I* 1 what Declination are a and 77 ? 
What stars are in the Crown ? What three small stars are on a 
line with /? ? What four small stars form a rhombus between 
and the Little Bear ? 

Plate IV. 

Name the constellations on this plate. 

How is Cassiopeia bounded ? What are the five principal stars 
and what figure do they form ? Which is nearest the pole ? 
What is the R. A. of (3 ? What three stars lie near the parallel 
of 60° ? How is the head marked ? 

What two small constellations lie between Cassiopeia and the 
pole ? Give their boundaries. 

Give the boundaries of Perseus. What is its extent in R. A. 
and Dec. ? What are the principal stars in this constellation, 
and how are they situated ? Where is Medusa's Head ? What 
stars are in the knees ? What in the hilt of the sword ? 

How is the Cameleopard bounded ? Of what kind of stars is 
it composed ? What is its extent ? 

How is the Lynx situated, and of what does it consist ? What 
small constellation lies south of it ? 

How is the constellation of the Great Bear bounded ? What 
figure is formed by the seven principal stars ? Draw this figure. 
What star is at the end of the tail? What star is next to it? 
What two stars point nearly towards the pole ? Which is nearest 
the pole ? What two stars of the third magnitude are on a line 
with (3 and S ? Give the situations of the small stars in the head 
and the two hinder feet of the bear. Give the R. A. and Dec. 
of a, y and e. 

What small constellation lies immediately south of the Great 
Bear ? How is it bounded, and of what is it composed ? 

Plate V. 

What are the principal constellations on this plate ? 

What are the boundaries of Pegasus ? What three bright 
stars form nearly a square with a of Andromeda ? In what R. A. 
are a and (31 In what Dec. are a and y ? Mention some of the 
stars in the head and neck. Where is e, and what are its R. A. 
and Dec. ? What stars are near (3 ? 

Where are the Fishes situated ? How are they connected ? 
What is the extent of this constellation ? 

How is Andromeda bounded ? What are the R. A. and Dec. 
of a in the head ? What three bright stars are in a right line ? 



360 QUESTIONS. 

What smaller stars lie in a line nearly parallel to and above this ? 
What star forms, with a and /?, a right-angled triangle? 

How is the Ram bounded ? What are the stars in the head ? 
Give the R. A. and Dec. of a and 0. Where is 8 ? 

What small constellation lies between the Ram and Andro- 
meda ? What one east of the Triangles ? What figure is formed 
by the stars a, b and c of the Triangles. 

Plate VI. 

Name the constellations on this plate. 

How is that of the Bull bounded ? What is its extent ? Whai 
are the R. A. and Dec. of a, or Aldebaran ? Mention the princi- 
pal stars in the head. What is this cluster called ? (See Plate 
XVI.) By what stars are the horns marked ? In what direc- 
tion are they from the Hyades ? In what R. A. and Dec. are 
the Pleiades, or Seven Stars ? What four small stars south-west 
of these ? 

What beautiful constellation lies south-east of the Bull ? How 
is Orion bounded ? What is its extent ? In what R. A. and 
Dec. are a, or Betelgeux, and /?, or Rigel? What three stars 
mark the belt, and how are they situated with respect to a and ? 
What stars are in the sword ? What one is just below the 
sword ? Where is y ? How is the shield marked ? Draw a 
figure of this constellation. 

Give the boundaries and extent of the Wagoner. What are 
the R. A. and Dec. of a, or Capella ? What star lies nearly on 
the same parallel 10° east of Capella ? How is the head marked? 
Mention some of the stars in the southern part of the Wagoner 

How are the Twins bounded? In what part are a and /?, or 
Castor and Pollux ? Which is farthest north ? What are the 
other five principal stars, and how are they situated ? Near what 
meridian is a ? By what parallel is it separated from /? ? 

How is the Little Dog bounded ? Give the R. A. and Dec. 
of a, or Procyon. What is the other principal star ? In what 
direction is it from Procyon ? In what from Castor ? 

What constellation lies south of the Twins and the Little Dog, 
and east of Orion ? What is its extent in R. A. ? 

How is the Crab situated ? What are the R. A. and Dec. of 
the cluster of stars called Prsesepe, near y 1 Where are a and /3 ? 

Plate VII. 

Name the principal constellations on this plate. 

What are the boundaries of Bootes ? What is the situation 



QUESTIONS. 361 

of a, or Arcturus? What are its R. A. and Dec? What two 
stars, the one in the leg and the other in the girdle, form an iso- 
sceles triangle with Arcturus ? What stars are above these two 
and nearly in a line with them ? Draw a figure representing the 
relative positions and distances of the nine principal stars. How 
many degrees apart are y and £ ? What stars are in the right 
or eastern leg ? What in the western ? What in the club ? 
What constellation lies east of the club ? 

How is the Northern Crown bounded ? Draw a figure repre- 
senting the principal stars. What do s, S, y, a, /? and $ form ? 
Of what magnitude is a, and what are its R. A. and Dec. ? 

What are the boundaries of the constellation Hercules ? What 
is its extent in R. A. and Dec. ? Where is a, or Ras Algethi 
situated ? In what R. A. and Dec. is it ? What two stars above 
it have nearly the same R. A. ? What is the distance between a 
and <5 ? Between a and n ? What two stars are near the meri- 
dian of 250° ? Between what parallels are they ? What two 
stars are near the parallel of 20°, and between what meridians 
are they ? Where is the Cerberus, and what are some of the 
stars in it? 

How is the Polish Bull bounded ? What are the principal 
stars, and where are they situated ? 

How is the Lyre bounded ? What are the R. A. and Dec. of 
a, or Vega ? What two small pairs of stars make, with it, an 
equilateral triangle ? Which of these is farthest north ? Where 
are /3 and yl What double star is near the centre of the Lyre ? 

Plate VIII. 

How is the Great Lion bounded ? Where is a, or Regulus ? 
What star lies about 5° north of it ? What star is 5° north-east 
of v ? What figure is formed by these three stars with £, n and e ? 
What star is in R. A. 166° and Dec. 16° north? What one is 
5° due north of this ? What are the R. A. and Dec. of /3, or De- 
nebola, in the tail ? Mention some of the most southern stars 
in this constellation. 

What small constellation lies south of the fore-legs, and west 
of the hind-legs, of the Lion ? 

How is the constellation of the Virgin bounded ? How is it 
divided by the equator ? What are the principal stars north of 
the equator ? What south ? What stars lie on or near the equa- 
tor ? On what parallel is a, or Spica, situated ? What is its R. 
A. ? What figure does it form with (3 of the Lion, and a of 
Bootes ? What two stars of the third magnitude are within 
this triangle ? What stars are in the southern wing ? What in 
the head ? What in the feet ? 



362 QUESTIONS. 

How is Berenice's Hair bounded ? What are the magnitudes 
of the stars of which it is composed ? 

Plate IX. 

How is the constellation of the Scales bounded ? What are 
the magnitudes and situations of the two principal stars ? Where 
are 6 and c ? 

What small constellation lies south of the Scales ? What four 
stars in it form a rectangle ? Which is the brightest ? 

What are the boundaries of the Serpent- bearer ? Where is a, 
or Ras Alhague, situated ? What two stars are below a, in the 
shoulders ? Where are rj and £ ? Name some of the other prin- 
cipal stars. 

Where is the head of the Serpent ? What stars are in and 
near the head ? Give the R. A. and Dec. of a ? What is the 
extent of the Serpent in R. A. and Dec. ? What is the R. A. and 
Dec. of the extremity of the tail ? 

Where is Sobieski's Shield ? 

How is Antinoiis bounded ? Name the principal stars, and 
their magnitudes. How are k and i situated with respect to each 
other ? 

Give the boundaries of the Eagle. Between what two stars 
is a, or Altair, situated ? On what parallel is y ? What two 
stars lie north-west of Altair ? 

How is the Dolphin bounded ? What figure is formed by the 
stars in the head ? What star lies on the parallel with y in the 
Eagle ? Of what magnitudes are these five stars ? In what R. 
A. and Dec. is yl 

How are the Fox, the Goose and the Arrow bounded ? What 
are the principal stars ? Their magnitudes ? Between what 
parallels do they lie chiefly ? 

In what direction is Equuleus from the Dolphin ? What do 
the stars a, /? and 6 form ? 

Plate X. 

Name the constellations on this plate. 

How is the Scorpion bounded ? What is its extent in R. A. 
and Dec. ? Draw a figure representing the principal stars in the 
body, and those in the tail. Where is a, or Antares, situated ? 
Where is /3 ? What two stars lie nearly in a line with these ? 
What three stars of the third magnitude lie in the end of the 
tail ? Near what meridian are they ? What stars are on the 
meridian of 250° ? 



QUESTIONS. 363 

In what direction is the Wolf from the Scorpion ? Mention 
some of the principal stars in the Wolf? What are their mag- 
nitudes generally ? 

What small constellation lies east of the Wolf? 

What one east of that and south of the Scorpion's tail ? Near 
what meridian are the two principal stars ? On what parallel 

is a? 

Where is the Telescope situated ? 

How is the Southern Crown bounded ? Of what magnitude 
are the stars composing it ? What figure do they form ? 

What are the boundaries of the Archer ? What four stars 
mark the bow? What three mark the arrow? Which way 
does the arrow point ? What stars are in the head ? Give the 
R. A. and Dec. of c Of p. 

Plate XL 

Name the constellations on this plate. 

What are the boundaries of the Goat, or Capricornus ? What 
is its extent in R. A. ? What are the R. A. and Dec. of the star 
? What double stars mark the two horns ? Where is 8 ? 
What four stars in the tail form a parallelogram ? 

What two small constellations lie south of the Goat ? Which 
of these is farthest east ? 

What constellations lie north of the Water-bearer ? What 
south ? What east, and what west ? What is its extent in R. 
A. and Dec. ? What stars mark the shoulders ? Of what mag- 
nitude are they? Mention some of the stars in the Urn and in 
the stream issuing from it. What small stars mark the western 
limit of this constellation ? What are the R. A. and Dec. of 8 ? 

What are the boundaries of the Southern Fish ? In what R. 
A. and Dec. is a, or Fomalhaut, situated ? What is its magni- 
tude ? What two stars of the third magnitude are there, and 
how are they situated with respect to Fomalhaut ? 

What small constellation lies south of the Southern Fish ? 
What are the principal stars in the Crane ? Near what parallel 
are a and ? 

How is the Sculptor's Shop bounded ? 

What small constellation lies south of the Sculptor's Shop, and 
east of the Crane ? 

Plate XII. 

Name the principal constellations on this plate. * 

How is the Whale bounded ? What is its extent ? Give V Qe 



364 QUESTIONS. 

R. A. and Dec. of a, and o. What four stars of the fourth 
magnitude form a trapezium on the breast of the Whale ? What 
four of the third magnitude between o and /3 ? What two be- 
tween a and o ? 

What two small constellations lie south of the Whale ? What 
is the principal star in the Chemical Apparatus, and how is it 
situated ? 

Give the boundaries of the River Po. What are the principal 
stars in the northern part ? 

Where is the Time-piece situated ? Where is the Graver ? 

What small constellation lies north of the River Po, and east 
of the Whale ? 

Where is the Sceptre, and of what does it consist ? How are 
they situated ? 

How is the Hare bounded ? What are the principal stars in 
it ? What are the R. A. and Dec. of a ? How are the ears 
marked ? 

Plate XIII. 

Name the constellations on this plate. 

What are the boundaries of the Dove ? What are the R. A. 
and Dec. of a ? What three stars are in R. A. 86° ? What 
double star is in the head ? 

What constellation lies south of the Dove ? 

How is the Great Dog bounded ? Name the most conspicuous 
stars. What are the R. A. and Dec. of a, or Sirius ? In what 
direction is this constellation from Orion ? Draw a figure repre- 
senting the eight principal stars ? What two of these are on the 
meridian of 94° ? 

What part of the Ship Argo is represented on this map ? How 
is it bounded on the north, east and west ? What three stars are 
on the meridian of 120° ? In what R. A. and Dec. are a and ? 
What stars lie between the parallels of 20° and 30° ? 

Where is the Printing Press situated ? 

What are the boundaries of the Compass ? 

Between what constellations is that of the Cat situated ? 

Plate XIV. 

Name the constellations on this plate. 
"V\ What is the extent of the Water Serpent in R. A. ? What 
ta 1 ' onstellations bound it on the north ? What on the south ? In 
nier.Hat R. A. and Dec. is a, or Cor Hydrse ? What are the stars in 



QUESTIONS. 305 

the head ? Under what constellation do they lie ? Between what 
parallels does the eastern part, or the tail of the Hydra, chiefly 
lie? 

How is the Air Pump bounded ? 

Where is Charles' Oak ? 

How is the Cup bounded ? Give the names and magnitudes 
of some of the principal stars. 

What constellation lies east of the Cup ? What bounds the 
Crow on the north and east ? Give the names and situations of 
the three principal stars. 

How is the Centaur situated ? What are the principal stars 
between the parallels of 30° and 40° ? What star is in R. A. 
180°, Dec. 50° S. ? 



THC IN9. 



Ce 



3^77-2 



